_fcfe*.le 





(1;.ss 1\Ki-90 



opfflglil X". 



COnKKlUT DKPOSIT, 



LECTURE -NOTES 

ON 

CHEMISTRY 

FOIl 

DENTAL STUDENTS 



INCLUDING 

DENTAL CHEMISTRY OF ALLOYS, AMALGAMS, ETC. 
SUCH PORTIONS OF ORGANIC ANB PHYSIOLOGICAL CHEMISTRY AS 

HAVE PRACTICAL BEARING ON THE SUBJECT OF DENTISTRY 

AN INORGANIC QUALITATIVE ANALYSIS WITH SPECIALLY ADAPTED 

BLOWPIPE AND MICROSCOPICAL TESTS, AND THE CHEMICAL 

EXAMINATION OF URINE AND SALIVA 



BY 

H. CARLTON SMITH, Ph G. 

Austin Teaching Fellow in Dental Chemistry and Lecturer on Physiological Chemistry 
at Harvard University Dental School 



FIRST EDITION 
FIRST THOUSAND 



KEW YORK 

JOHNT WILEY & SOTsTS 

Londok: CHAPMAN & HALL, Limited 

1906 



'-? 



\^ 



LIBRARY of CONGRESS 
Two CoDies Received 

JUN 4 1906 

popy right Entry 
CLASS ' CL 'XXC. No, 

/(J C, 9 3x^ 

COPY B. 



7^ 



Copyright, 1906 

By 

H. CARLTON SMITH 



ROBERT DRUMMOND, PRINTER, NEW YORK 



PEEFACE. 



The arrangement of this book follows rather closely the 
lecture course in Dental Chemistry as given by the author at 
the Harvard Dental School. It has been the aim of these 
lectures to give the student, as concisely as possible, such por- 
tions of the various branches of chemistry as are most likely 
to be of value in practical work. 

Simplicity of manipulation has in some cases been con- 
sidered of greater practical value than extreme accuracy, 
especially in the chapter on Quantitative Analysis. The 
volumetric processes being given as a rule, rather than the 
more exact but more difficult gravimetric methods. 

The usual equipment of a dental laboratory has been borne 
in mind, and considerable prominence given to the simpler 
analytical tests made in the dry way by means of few reagents. 

Recent text-books and current literature have been very 
generally consulted. New tests have been verified so far as 
possible — often modified — before being recommended to the 
student. 

The U. S. Dispensatory and the Newer Materia Medica, as 
given in the Druggists' Circular, have been drawn upon in the 
sections on Local Anaesthetics; Hall's and Essig's Chemistries 
in the section on Allo3^s and Amalgams. 

A chapter on Organic Chemistry has been introduced, de- 
signed to furnish an understanding of this branch of chemical 



IV PREFACE. 

science, which will enable the student to better comprehend 
the physiological chemistry which follows. 

The chapter on the Analysis of Saliva is one which is of 
necessity incomplete and imperfect. The investigations being 
at present carried on along the lines suggested by Dr. Joseph 
Michaels of Paris and Dr. Kirk of Philadelphia are opening up 
fields of research of the greatest magnitude and of utmost im- 
portance, and they can only be touched upon in this work. 

The atomic weights given are from the international atomic 
weights for 1905. = 16. 

In the chapter on Physiological Chemistry the author wishes 
to particularly acknowledge his indebtedness to Professor 
Wm. B. Hills of the Harvard Medical School, who furnished 
the majority of the laboratory experiments for this portion 
of the work. 

H. C. S. 



TO THE STUDENT. 



As the student of dentistry takes up the study of chemistry, 
it is necessary that he should reaUze that the course will be of 
value to him in the ability acquired to draw correct inferences 
from observed phenomena, and in the attainment of accuracy 
and delicacy in manipulation, fully as much as in amount of 
chemical knowledge obtained. In other words, he must do his 
own thinking, carry out his own processes and experiments, 
make his own analyses, or the time spent will be little better 
than wasted, for the chemical facts which may happen to be 
remembered will be of slight benefit in the work to which every 
student, worthy of the name, aspires, that of developing, 
broadening, and elevating the profession which he has chosen 
as his own. 

The course of study outlined in this book is designed to 
furnish the starting-points in the various branches of chemistry, 
which will be of practical value in solving the problems constantly 
presenting themselves for consideration. It is hoped that these 
starting-points may, in the future, serve as the basis for work 
along the lines of original research, and that the best interests 
of dental science may be furthered thereby. 

It is supposed that the student has had the advantage of a 
laboratory training in general chemistry, and is conversant 
wdth the properties and methods of preparation of the so-called 
non-metallic elements, also with the fundamental principles 
and laws of theoretical and physical chemistry. That he is 



VI TO THE STUDENT. 

familiar with laboratory apparatus, such as test-tubes, beakers, 
crucibles casseroles, evaporating-dishes, retorts etc., and that 
he has had some experience in the ordinary processes of pre- 
cipitation, filtration, evaporation, distillation, sublimation, and 
crystallization. 

If there is any feeling of insufficient preparation it is strongly 
advised that a short course of preliminary study be taken. 
Chemistry furnishes the groundwork of all branches of medical 
science to a much greater extent than we are apt to think, 
and even in the study of subjects which in times past have 
been carried on with little reference to chemistry, we now see 
the desirabiUty if not the necessity of a good general know- 
ledge of chemical science. The physiologist and the bacteri lo- 
gist are to-day turning to chemistry for the ultimate solution 
of their most perplexing problems. H. C. S. 



TABLE OF CONTENTS. 



PAGE 

Preface iij 

To THE Student v 

PART I. 

QUALITATIVE ANALYSIS. 

Section I. The Metals 1 

AAalysis, Groups I to VI. 3 

Outline Schemes for Analysis 38 

Section II. Analytical Test for the Acids 41 

Section III. Analysis in the Dry Way 50 

Blowpipe Tests 55 

PART 11. 
DENTAL METALLURGY. 

Section I, The Metals 59 

Section II. Alloys 64 

Section III. AmalgaxMS 67 

Effects of Various Metals in Amalgams 71 

Tests for Amalgams. 73 

Section IV. Dental Cement 75 

Section V. Solders 79 

Fusible Metals 85 

Section VI. Recovery of Residue 86 

PART III. 

VOLUMETRIC ANALYSIS. 

Standard Solutions 94 

Quantitative Analysis of Dental Alloys 102 



viii TABLE OF CONTENTS. 

PART IV. 
MICROCHEMICAL AiNALYSIS. 

PAGE 

Local Anesthetics 108 

Teeth and Tartar 118 

PART V. 

ORGANIC CHEMISTRY. 

Section I. The Hydrocarbons and Substitution Products 122 

Section II. Alcohols 130 

Section III. Ethers , 135 

Section IV. Organic Acids 143 

Section V. Cyanogen Compounds 152 

Section VI. Closed-chain Hydrocarbons 161 

PART VI. 

PHYSIOLOGICAL CHEMISTRY. 

Section I. Ferments ley 

Section IL Carbohydrates , 170 

Section III. Fats and Oils 177 

Section IV. Proteids 180 

Section V. Blood, Bone, Muscle, etc 193 

PART VII. 

DIGESTION. 

Section I. Saliva, Properties and Constituents 203 

Section II. Analysis of Saliva 210 

Crystals from Dialyzed Saliva 212 

Section III. Gastric Digestion , 217 

Section IV. Pancreatic Digestion and Bile. 222 

PART VIII. 

URINE. 

Section I. Physical Properties of Urine 226 

Section II. Normal Constituents 230 

Section HI. Abnormal Constituents 237 

Urinary Sediment 245 

Interpretation of Results 251 

Appendix 255 



DENTAL CHEMISTRY. 



PART I. 
QUALITATIVE ANALYSIS. 



SECTION I.— THE METALS. 

The metals, from certain physical properties, have been 
variously classified. Thus in the older books we read of the 
Nohle metals, those unaffected by heat, as gold, silver, and 
platinum; the Base metals, the Bastard metals, those easily 
crystallizable, as antimony and zinc; the Metalloids, sodium 
and potassium. 

As the fact became better understood that the properties 
of metals were to a considerable extent dependent upon con- 
ditions of temperature, pressure, etc., the old classifications 
were less and less used, until now we are very apt to group 
them according to the chemical behavior of their salts, irrespect- 
ive of their properties as metals. Thus Ag, Pb, and Hg (Mer- 
curous) form a group of metals whose chlorides are insoluble 
in water or dilute acids. These metals may consequently be 
thrown out of solution or precipitated by the addition of HCl 
to any solution of their salts. We therefore let Ag, Hg', and 
Pb constitute the First Analytical Group, and HCl is the First 
Group Reagent, • 



2 , QUALITATIVE ANALYSIS. 

In like manner we find a group of nine metals that are 
precipitated from dilute acid solution by hydrosulphuric acid 
(H2S). These metals are Cu, Cd, Bi, Hg, As, Sb, Sn, Au, 
and Pt, and constitute the Second Analytical Group, and H2S 
is the Second Group Reagent. 

The fact that the sulphids formed by the first four of these 
metals are insoluble in ammonium sulphid, and those formed by 
the last five are soluble, furnishes a simple method of separating 
this group into two parts, a and h : 

Pb,* Cu, Cd, Bi, and Hg constituting Group II (a) and 

As, Sb, Sn, Au, and Pt, Group II (b). 

Thus the metals are divided into various analytical groups, 
each with its own peculiar group reagent. Different groupings 
are possible, and hardly any two analysts will employ exactly 
the same scheme for identifying all the metals, although the 
following group divisions are generally used: 

Analytical Grouping. 

Group I. — ^Ag, Pb, and Hg^ Metals that form insoluble 
chlorids and precipitated from aqueous solution by HCl 
(the group reagent). 

Group II (a).— Cu, Cd, Bi, Hg'^ and Pb. Metals that form 
sulphids insoluble in dilute HCl solution and also in- 
soluble in ammonium sulphid. 

Group II (h). — As, Sb, Sn, Au, and Pt. Metals that form 
sulphids insoluble in dilute HCl but soluble in yellow 
ammonium sulphid, or alkaline hydrates. 

Group III. — Fe, Al, and Cr. In solutions free from H2S 
and which do not contain phosphoric, oxalic, tartaric, 
and certain other organic acids, these three metals may 
be separated by ammonium hydrate, NH4OH. 

Group IV. — Co, Ni, Mn, and Zn. Metals forming sulphids 

* Lead is included in this group because it is not entirely separated as a chlorid 
in Group I; traces of it remaining in solution even after addition of HCl. 



THE METALS. 3 

soluble in acid but insoluble in alkaline solution. Ammo- 
nium sulphid, (NH4)2S, is the group reagent. 
Group V. — Ba, Sr, Ca, and Mg * Metals forming carbonates, 
insoluble in alkaline solutions. The group reagent is 
ammonium carbonate, (NH4)2C03. 
Group VI . — K, Na, Li NH4. Metals which cannot be 
precipitated by any single reagent and for which it is 
necessary to make individual tests. 
It is our purpose to take up the study of the metals accord- 
ing to their analytical grouping: first, the deportment of 
their salts in solution; later, the metals themselves and their 
specific application to dentistry. 

REACTIONS OF GROUP I. 
Silver, Ag (Argentum). 

Atomic weight 107.93. Occurs free also as various sul- 
phids, silver glance, Ag2S, and in combination with the sul- 
phids of antimony, lead, and copper. 

Silver is readily soluble in nitric acid with formation of 
AgNOs, colorless crystals, without water of crystalHzation. 

Make the following tests with a weak solution of AgNOa 
(about 2%). Write the reactions and enter color and solu- 
bility of each precipitate formed in laboratory note-book.f 

AgNOs with HCl gives a white curdy precipitate of AgCl 
which darkens by action of sunlight. If Ag solution is very 
dilute, the precipitate will assume the curdy appearance and filter 
more easily if it is heated and rotated quite rapidly in the test- 

* In the process of analysis, magnesium is held in solution by the presence 
of NH4CI and is not thrown out as a carbonate with the other three members 
of the group. 

t The author uses mimeograph copies of these experiments with spaces for 
the reactions and colors of precipitates, which are filled out without reference 
to the book and handed in by the student at the close of the laboratory exercise. 

These reactions have purposely been confined to such as may be applied 
to the processes of analysis. 



4 ' QUALITATIVE ANALYSIS. 

tube. Allow the precipitate to settle. Decant the liquid 
carefully, divide precipitate into two parts and test its solu- 
bility in dilute nitric acid, also in ammonia-water. 

AgNOa with KBr gives a white precipitate of AgBr, less 
easily soluble in ammonia than the AgCl. 

AgNOs with KI gives a pale yellow precipitate of Agl, 
insoluble in ammonia. 

AgNOs with H2S gives a black precipitate of Ag2S. 

AgXOa with K2Cr04 gives a red precipitate of AgCrO^ in neutral solution. 
Test the solubility of x\gCrO, in NH.OH, HCl, and HNO3. 

Mercury, Hg (Hydrargyrum). 

Atomic weight 200. Occurs as red sulphid, cinnabar, and 
in small quantities amalgamated with silver or gold or com- 
bined with chlorin or iodin. It is the only metal which is 
liquid at ordinary temperatures, soHdifying at —39°. In study- 
ing the reaction of mercurous salts it is convenient to use a solu- 
tion of the nitrate, made by treating mercury with cold dilute 
HNO3. (This solution of mercurous nitrate, upon standing, 
will be found to contain more or less mercuric nitrate, unless 
care is taken to keep excess of mercury in the bottom of the 
bottle.) 

HgNOs with HCl gives a white precipitate of HgCl (calomel). 
After the precipitate has settled decant the liquid and test the 
solubility of the HgCl in ammonia water. Does it dissolve? 
How does its behavior differ from that of AgCl? 

Alkaline hydroxids form with mercurous salts the black 
oxid Hg20; a preparation of which, made with lime-water 
and calomel, is known as '' blackwash." 

Lead, Pb (Plumbum). 

Atomic weight 206.9. Occurs as sulphid (galena), PbS, also 
in lesser quantities as native carbonate and sulphate. Lead 
is soluble in nitric or acetic acid, forming Pb(N03)2 or 



THE METALS. O 

Pb(C2H302)2. A 2% solution of the nitrate maybe used in the 
following tests : 

Pb(N03)2 with 2HC1 gives white precipitate of PbCl2. 
Test its solubility in hot water and in NH4OH. 

Pb(N03)2 with NH4OH gives white precipitate of Pb(0H)2 
insoluble in hot water. 

Pb(N03)2 with H2S gives black PbS. Test solublility of 
precipitate in warm dilute HNO3. 

Pb(N03)2 with H2SO4 gives white precipitate of PbS04, 
forming slowly in dilute solutions. 

Pb(N03)2 with K2Cr04 (or K2Cr207) gives a yellow precipi- 
tate of PbCr04. 

Pb(N03)2 gives with KI a yellow recipitate, Pbl2. Avoid 
excess of the potassium iodid. 

By the application of the foregoing reactions we may formu- 
late a scheme for the separation and identification of the metals 
of Group I as follows : 

Analysis of Group I. 

(Ag, Pb, Hg'.) 

To the clear solution to be tested add slowly dilute HCl as 
long as any precipitation occurs. Filter and wash the precipi- 
tate once with cold water, add this washing to filtrate to be tested 
for remaining groups; then wash precipitate on the paper with 
several small portions of hot water. 



AgCI and HgCl remain undissolved. 




PbClg is in the hot-water solution. 



Divide this hot-water solution into three parts and make 
three of the following tests for lead : First, with K2Cr207, which 
gives yellow precipitate of PbCr04. Second, with H2SO4, 




6 QUALITATIVE ANALYSIS, 

giving a white precipitate of PbS04. Third, with H2S water, 
giving black precipitate of PbS. Fourth, with KI, which 
forms a yellow precipitate of Pbl2. Write these reactions. 

To undissolved residues of Hg and Ag chlorids add warm 
NH4OH. 

Hg remains on the paper, black, as HgNHgHgCl. 

Ag is dissolved by the XH^OH and may be precipitated as 
AgCl by adding HXO3 to acid reaction. Presence of Hg 
in the black residue may be confirmed as in Group II 
(page 17). 

QUESTIONS ON GROUP I. 

Why wash the precipitated chlorids only once with cold 
water? 

Why is it necessary to wash the PbCl2 out with hot water 
before using ammonia? 

Why is the ammonia used? 

How does HNO3 reprecipitate silver chlorid f 

REACTIONS OF GROUP II. 

Copper, Cu (Cuprum). 

Atomic weight 63.3. Occurs free in vicinity of Lake Superior, 
also in western United States, Chili, and Spain as sulphids, 
copper pyrites, CuFeS2, and copper glance, CU2S. Malachite 
green and malachite blue are native basic carbonates of Cu. 
Copper dissolves easily in nitric and acetic acid with difficulty 
in HCl, and heated with H2SO4 forms CUSO4 with the evolution 
of SO2. It forms two series of salt, cuprous (comparatively 
unimportant) and cupric, the common salts of which are the 
sulphate, acetate, and nitrate, while the chlorid and carbonate 
are frequently used. 

Salts and solutions of Cu are usually blue or green. 

A 1% solution of CUSO4 will give the following reactions: 



THE METALS. 7 

CUSO4 with H2S gives CuS, brownish-black sulphid; test 
its solubiHty in (N 114)28 and in warm dilute HNO3. 

CUSO4 with NH4OH (one or two drops of reagent) will 
precipitate Cu(0H)2 bluish white. Add more NH4OII to same 
test-tube and note the result. To this clear solution add a 
sufficient amount of dry KCN to completely decolorize the 
liquid. Then add to the mixture some H2S water. Is the black 
CuS thrown out? The behavior of Cu solutions thus treated 
is due to the formation of double salts; the solution in am- 
monia being due to a compound of CU8O4 and NPI3, and the 
decolorization of the blue solution to one of Cu(CN)2 and KCN. 

CUSO4 with K4FeCy6 (potassium ferrocyanid giv(s in 
acetic acid solution a red-brown precipitate of Cu2FeCy6. 

Metallic zinc or iron will precipitate copper from solution. 
Hold a knife-blade in a solution of CUSO4 for a few seconds. 

Mercury in mercuric combination. 

A 2% solution of corrosive sublimate (HgCl2) may be used 
in demonstrating the reactions of dyad mercury. 

HgCl2 with H2S gives first a white precipitate, turning 
yellow, brown, and finally black as proportion of H2S increases. 
The black precipitate only is mercuric sulphid, and care must 
be taken to add H2S till this compound is produced. 

Test the solubility of HgS in (NH4)2S and HNO3. 

To HgCli solution add SnCl2. The mercuric chlorid is 
reduced to mercurous chlorid (HgCl, white) or metallic mer- 
cury (Hg, gray), according to proportion of the tin salt used: 
2HgCl2+SnCl2 = 2i/^CZ + SnCl4 or HgCl2 + SnCl2 = % + SnCl4. 

HgCl2 with KI gives red Hgl2, easily soluble in excess of 
either of the reagents. 

Alkaline hydroxids or carbonates precipitate from soluble 
mercuric compounds the 3^ellow oxid, HgO. A preparation 
made from mercuric chlorid and lime-water is known in phar- 
macy as '^ yellow- wash." 

HgCl2 with NH4OH gives white precipitate of (XH2Hg)Cl, 



8 QUALITATIVE ANALYSIS. 

known as ^Svhite precipitate." ^'Red precipitate" is a term 
sometimes used to designate the red oxid of mercury, HgO, 
made in the dry way. 

Bismuth, Bi. 

Atomic weight 208.5. Bismuth does not occur in large 
quantities, but is usually found in the free state. Small amounts 
are obtained from the oxid, Bi203, bismuth- ochre, and from 
the sulphid, Bi2S3. 

It is easily identified by means of blowpipe test on plaster 
with S and KI. 

The most available salt is the nitrate, insoluble in water 
unless strongly acidulated. 

Use a 2% solution of Bi(N03)3 in the following tests: 

Bi(N03)3 with NH4OH gives white precipitate of bismuth 
hydroxid, (BiOH)3. 

Bi(N03)3 with H2S precipitates Bi2S3, brownish black, in- 
soluble in (NH4)2S, but soluble in warm dilute HNO3. 

Bismuth forms with water insoluble basic salts, according 
to the following equation: 

Bi(N03)3 + H2O = BiON03 + 2HNO3. 

This may be demonstrated by allowing a few drops of bis- 
muth solution to fall into a comparatively large amount of 
H2O (two to six ounces). A white cloud of insoluble oxy- 
salt may be observed settling through the clear water. This 
may be employed as a final test for Bi in the course of sys- 
tematic analysis. 

Cadmium, Cd. 

Atomic weight 112.4. Occurs associated with Zn in zinc 
blend. It is much more easily volatile than zinc, and advan- 
tage is taken of this fact in effecting its separation from that 
metal. 



THE METALS. 9 

A 2% solution of the sulphate or nitrate may be used in 
studying the deportment of cadmium salts. 

CdS04 with H2S gives a bright yellow sulphid, CdS, soluble 
in dilute nitric acid. 

CdS04 with (NH4)2S also precipitates the yellow sulp!i;d. 

Cadmium sulphid forms slowly and, in presence of Cu or 
other second-group metals, may escape precipitation if the 
reagent is added in insufficient quantity. 

Arsenic, As. 

Atomic weight 75.0. Occurs associated with copper and 
iron sulphids, as arsenical pyrites, FeAs.FeS2; as native 
sulphids, orpiment, AS2S3, and realgar, AS2S2; also to some 
extent as the trioxid, AS2O3. 

Arsenic forms two series of salts, the arsenious. As''', and 
arsenic, As^, and it also acts as an acid radicle forming arse- 
nious and arsenic acids. In the process of analysis, arsenic 
compounds whether acid or basic are reduced to arsenious by 
action of H2S. It is most easily obtained in the form of the 
trioxid, AS2O3, also known as arsenious acid or white arsenic. 

A solution for studying the reactions of arsenic (As'") is 
conveniently made by dissolving about 15 grams of white 
arsenic in dilute NaOH solution by aid of heat, then diluting 
to one liter and acidifying slightly with HCl. 

To an arsenious solution, which may be represented by 
AsCls, add H2S water. A lemon-yellow precipitate of AS2S3 
will be thrown down. Test the solubility of this precipitate 
in yellow ammonium sulphid and ammonium carbonate. 

To the alkaline solution of the sulphid add excess of HCl: 
AS2S3 is precipitated. 

To an arsenious solution add (NH4)2S in repeated small 
portions. 

In neutral solution, as of sodium arsenite, Na3As03 silver 
nitrate will throw down yellow silver arsenite, soluble in excess 
of nitric acid or ammonia. 



10 QUALITATIVE ANALYSIS. 



SPECIAL TESTS FOR ARSENIC. 

Reinsch's Test for arsenic, applicable to any solution whether 
organic or not, and very valuable for a preliminary test, is 
made as follows : place the solution or mixture to be tested in a 
porcelain dish, acidify strongly with HCl, and add a small strip 
of bright copper foil (cleaned in dilute HNO3 and thoroughly 
washed in distilled H2O) and boil for ten or twenty minutes, 
adding sufficient water to replace loss by evaporation. Remove 
the copper foil : a dark gray to black coating is an indication 
of arsenic but not conclusive, as some other substances give 
similar deposits, mercury and antimony in particular. 

To prove the presence of As, roll the foil as tightly as possible 
and introduce into the bulb of a small glass matrass. (Fig. 1.) 



Fig. 1. 

Heat the bulb over a very small luminous flame, when crystals 
of AS2O3 (tetrahedral or octahedral) will deposit in the con- 
stricted portion of the tube, and may be identified by micro- 
scopical examination. If the test is carried out in this way, 
there will be sufficient air in the matrass for the formation of 
the oxid and it becomes much more delicate than if heated in 
the ordinary open tube as often recommended. 

Gutzeit's Test is made by placing the suspected solution in a 
test-tube, acidifying with H2SO4, adding a few pieces of arsenic- 
free zinc, and, as hydrogen begins to be given off, placing over 
the mouth of the tube a piece of filter-paper carrying a drop of 
a strong solution of AgNOa. The presence of arsenic is indicated 
by the darkening of ihe moistened filter-paper in accordance 
with the following reactions: 

The nascent H liberated by action of the Zn upon the acid 
forms with any As present the gaseous AsHs which, in contact 
with the filter-paper wet with AgNOa solution, produces a brown 



THE METALS. 11 

or black stain of metallic Ag, while the As becomes arsenious 
acid, II3ASO3. The stain may possibly be yellow by formation 
of a compound of silver arsenide and silver nitrate, but as a rule 
moisture is present in sufficient amount to insure the decom- 
position of this compound. 

Antimony will give a similar brown or black stain (not yel- 
low), but presence of As may be conclusively demonstrated by 
making Fleitmann's Test, which is conducted in the same way 
as the preceding, except that the hydrogen is evolved in alkaline 
solution, either by means of Zn and strong KOH solution 
(Zn+2KOH = K2Zn02 + H2) or by sodium amalgam (made 
with arsenic-free mercury) and water (NaHg^ + H20 = NaOH 
+Hg + H). In this case the SbHs is not jonned; so a stain thus 
obtained constitutes a positive test for arsenic. 

TheMARSH-BERZELius Test for arsenic is the most delicate 
of all and the one to which we resort in detecting As' in the saliva 
or the urine. By this method one two-hundredth of a milligram 
or about 1/12S00 of a grain can be easily shown as a brown 
deposit in the constricted tube at about the point K, Fig. 2. 
The apparatus used in this test is shown in Fig. 2, and consists 
of a small Erlenmeyer flask, or wide-mouth bottle, fitted as a 
hydrogen generator A, and connected with a drying- tube B 
filled with fused calcium chlorid, then with a tube of hard glass 
C drawn out to a very small diameter for half its length. 

The generator A is charged with arsenic-free zinc, and 
dilute sulphuric acid (1/5) introduced through the thistle- tube 
E. After all air has been driven from the apparatus, light the 
escaping H at T, then the Bunsen burner D, and allow the 
generator to run for about twenty minutes, thus making a. 
blank test of apparatus and reagents; if at the end of this time 
the hard glass is perfectly free from any deposit, the suspected 
liquid, which must have been freed from organic matter (process 
described in detail in chapter on Urine Analysis) may be intro- 
duced in portions of about 10 c.c. each. 

The flame should be spread somewhat so as to heat at least 



12 



QUALITATIVE ANALYSIS. 



1 inch of the glass tube. This may be accomplished, in the 
absence of a burner-tip, by placing an inverted V-shaped piece 
of asbestos board 1 inch wide over the heated part of the tube. 

The presence of arsenic increases the evolution of hydrogen, 
and unless the solution is added gradually the AsHs may be 
driven so rapidly past the flame as to escape decomposition, or 
the tube may become heated to such an extent that arsenic will 
not be deposited. 

The escape of As at T may be noticed by the bluish color of 
the flame and by the characteristic garlic odor. 




Fig. 2. 



Antimony is similarly deposited as a dead-black stain 
instead of brown-black, and as Sb is less easily volatile than As 
the deposit will be nearer the flame, possibly on both sides of 
the flame. (For further differences between As and Sb see 
tests given on page 14.) 

Arsenic compounds (As^), as Na2HAs04, are of but little 
interest from the dentist's standpoint. 

All arsenic compounds are reduced by nascent H to arsenious 
combinations, then to elementary As, then to AsHs (arsine); 
hence the special tests given for arsenious compounds are 
applicable. 

Free chlorin, nitric acid in alkaline solution, and potassium 
ferricyanid oxidize arsenious compounds to arsenic, and in this 



THE METALS. 13 

condition the As is not easily volatilized and organic matter 
may be destroyed by deflagration (in presence of excess of ni- 
trates) with but slight loss of arsenic. 

Antimony, Sb (Stibium). 

Atomic weight 120.2. Occurs native in Australia, and as 
the sulphid, Sb2S3, known as Stibnite. 

The most common compound of antimony is the double 
tartrate of antimony and potassium (KSbOC4H406), known 
as tartar emetic. A 2% aqueous solution may be used in the 
following tests: 

To an antimony solution represented by SbCls add H2S 
water: Sb2S3 is precipitated orange-red. Test solubility of the 
precipitate in (NH4)2S and in (NH4)2C03. 

How does it differ from arsenic? 

Upon the addition of HCl in excess to the ammonium sul- 
phid solution the Sb is reprecipitated, but not necessarily as 
Sb2S3, but more usually as Sb2S5 or a mixture of the two 
sulphids. 

Salts of antimony tend to form oxycompounds and are 
held in solution by excess of acid. The antimonious chlorid, 
SbCls, in solution with HCl is precipitated by excess of water 
as a white oxychlorid, Sb4Cl205, also known 
as '^ powder of Algaroth." The antimonic 
chlorid in like manner precipitates the 
antimonic oxychlorid, SbOCla. Demon- 
strate by turning 1 or 2 c.c. of SbCla solution 
into a large excess of water. 

Marsh's test for As (or Sb) consists of 
a simple hydrogen generator with glass tip 
for burning the gas as shown in Fig. 3. In 
this apparatus Sb and As are converted 
into the gaseous hydrides, AsHa and SbHa, ^^^' ^' 

and if a piece of cold porcelain is pressed down upon the 
flame. As or Sb will be deposited as metallic stains (mirrors) 




14 QUALITATIVE ANALYSIS. 

upon the porcelain. To distinguish between As and Sb spots, 
the following tests will suffice: 

Arsenic. Antimony. 
Brown-black, lustrous spots. Dead brown or black surfaces. 
Soluble in solution of hypo- Insoluble in solution of hypo- 
chlorite of Hme or soda. chlorite of Ume or soda. 
Easily volatiHzed. VolatiUzed at red heat. 

Antimony may be retained in the generator by the intro- 
duction of a piece of platinum-foil; the Sb being precipitated 
upon the platinum, to which it adheres quite strongly. 

Tin, Sn (Stannum). 

Atomic weight 119.0. Cassiterite, or tin-stone, nearly pure 
Sn02, is by far the most important source. The free metal 
has been found associated with gold. 

Tin, hke arsenic and antimony, forms two series of salts, 
the stannous (Sn'') and the stannic (Sn^^) . A little HCl treated 
with excess of granulated tin till hydrogen is no longer given 
off furnishes a solution of stannous chlorid suitable for the 
following experiments : 

SnCL with H2S gives brown precipitate of SnS, soluble 
in (NH4)2S, insoluble in (NH4)2C03. 

SnCl2 with HgCl2 gives a white or gray precipitate as 
explained on page 7 under ^'Mercury" and is used as a test 
for presence of mercury. It may also be used as an alkaloidal 
precipitant. 

Strong solutions of SnCl2 in presence of metallic Sn keep 
fairly well, but dilute solutions without an excess of tin oxidize 
very rapidly to stannic combinations and cease to be of value 
as reagents. 

MetaUic tin is not dissolved by HNO3, but is converted into 
a white, insoluble metastannic acid. This acid, upon standing, 
changes to normal stannic acid which is easily soluble in acids; 
hence, in making use of this reaction in the analysis of amalgam 



THE METALS. 15 

alloys, it is not well to allow the nitric acid solution of the 
alloy to stand too long before filtering. 

Metallic zinc thrown into a tin solution will precipitate 
the tin as follows: SnCU + Zn^ZnC^ + Sn. 

This reaction is used in the separation of tin from antimony 
in the second group; and in order to obtain the tin in soluble 
form, suitable for a final test, it is necessary to add HCl suffi- 
cient to first dissolve all the Zn present; otherwise it may 
remain adhering to the zinc. 

Gold, Au (Aurum). 

Atomic weight 197.2. Usually found uncombined, but 
mixed with various impurities. 

Gold is insoluble in simple acids, but may be dissolved in 
nitrohydrochloric acid (aqua regia) with formation of auric 
chlorid. Gold also unites easily with Br or I, forming AuBrs 
or Auls. A half per cent solution of AuCla may be used in 
the following tests: 

H2S with AuCls gives dark brown AU2S3 (auric sulphid) 
soluble in yellow ammonium sulphid." 

Gold is reduced to the metallic state by many of the other 
metals, as Pb, Cu, Ag, Sn, Al, Sb, Fe, Mg, Zn, and Hg; also 
by ferrous sulphate, stannous chlorid, and oxalic acid. 

Add a freshly prepared solution of ferrous sulphate to a 
little acid solution of AuCla. Gold is precipitated as follows: 
AuCls + 3FeS04 = Au + Fe2 (SO4) 3 + FeCla . 

Stannous chlorid precipitates from gold solution, the " purple 
of Cassius," consisting of a mixture of gold and oxid of tin. 
.Gold is only slowly precipitated by oxalic acid, but, as Pt 
is not precipitated at all by this reagent, it is possible to sepa- 
rate Au and Pt in solution as chlorids by this means. 

KI will give a dark-green precipitate of Aul2 provided the 
KI is in excess; if the gold is in excess, the precipitate is apt 
to be the yellow Aul (aurous iodid). In the presence of a 
considerable excess of KI the Aula is kept in solution as the 



16 QUALITATIVE ANALYSIS. 

potassio-auric iodid, KIAuIs. The reduction of this double 
salt by sodium thiosulphate is made the basis of the method 
to determine the quantity of Au in a given alloy, as described 
in the chapter on Volumetric Analysis. 

Platinum, Pt. 

Atomic weight 194.8. Platinum solubilities are similar to 
gold; aqua regia forms the chlorid PtCU. 

PtCl4 + H2S gives a precipitate of sulphide of platinum 
almost black, soluble in yellow ammonium sulphid. 

Platinum solution with NH4CI precipitates yellow ammo- 
nium platinic chlorid, (NH4)2PtCl6, crystalline. Potassium 
chlorid also gives a yellow crystalline precipitate ofK2PtCl6,. 
isomorphous wdth the ammonium compound. (Plate I, Figs. 1 
and 5). These reactions may be made quantitative by using: 
neutral, fairly concentrated solutions and adding an equal 
volume of alcohol. 

Both of these double salts are soluble in excess of alkali 
and reprecipitated by HCl. 

Stannous chlorid reduces PtCU to PtCb but forms no 
precipitate. Metallic Zn will precipitate platinum as a fine 
black powder or spongy mass. 

Separation 0} parts (a) aiid (b) of Group II. 

A portion of the clear filtrate from group I containing a 
slight excess of HCl is tested for metals of group II by the 
addition of H2S water.* 

If a precipitate is obtained, warm the ichole of the solution 
and pass in H2S gas for from three to five minutes, which 
precipitates all metals of the group as sulphids. Filter. 

Break point of filter-paper with glass rod and wash group II 
into beaker with warm (NH4)2S; digest hot for a few minutes. 

• * A preliminary test is made on a part of the solution because in the absence 
of Group II the analysis of Group III can be made more easily without th& 
presence of HjS. 



THE METALS. 17 

Filter and wash the precipitate till wash-water shows only 
traces of CI. Throw away all wash-water except the first. 



Group II (a). Cu, Cd, Bi, Hg and Pb. 
Group II (6). As, Sb, Sn, Au, and Pfc. 

Analysis of Group II (a). 
Dissolve the precipitate off the paper with hot dilute HNOj 

Hg, if present, will remain on paper, black. 
Filtrate contains nitrates of Pb, Cu, Cd, and Bi 





Test black residue on paper for Hg'' by dissolving in aqua 
regia and precipitating with SnClo. For reaction between SnCl2 
and HgCU see page 7. Aqua regia may be made by mixing 
two or three parts of HCl with one of HXO3. Free CI is liberated 



which dissolves the HgS as HgClo. 



SHCl + HXO3 = XOCl ^ 2H2O + CI2. 

If lead was present in Group I, the filtrate above will contain 
traces which must be separated by adding a few drops of H2SO4 
and allowino; to stand at least fifteen minutes. Filter. 



PbSO^ remains on paper. 



filtrate contains Cu, Cd, Bi. 




18 



QUALITATIVE ANALYSIS. 




To the filtrate add NH4OH till alkaline; Bi separates as 
Bi(0H)3, white. Filter. 



Bi(0H)3 



Cu and Cd. 



Divide the filtrate (Cu and Cd) into two parts. A blue color 
indicates presence of Cu. With one part test for Cu by making 
it acid with acetic acid and adding K4FeCy6, which will give 
a brown precipitate of Cu2FeCy6. With the other part test 
for Cd by adding sohd KCN very carefully till all blue color 
has disappeared; then a little H2S water will give a yellow 
precipitate of CdS if cadmium is present. 

Analysis of Group II (5). 

To the ammonium sulphid add HCl till acid. A very fine 
white precipitate may be sulphur only. 

Filter and wash. Throw away wash-water. Pierce filter 
and wash sulphids into large test-tube or small beaker. Add 
10 c.c. of (NH4)2C03 and heat for a few minutes. Filter. 



Sb, Sn, Au, Pt sulphids. 



Arsenic sulphid. 



Add HCl and Zn and make Gutzeit's test (page 10) and 
if necessary Fleitmann's (page 11) or Marsh's (page 13). 

Dry this precipitate upon paper and place paper and precipi- 
tate in a porcelain evaporator, add concentrated HCl and heat. 
(This must be done under the hood.) Dilute and filter, when 
Au and Pt will remain undissolved. 




THE METALS. 19 



Sb and Sn. 




Au and Pt. 



To the Sb and Sn solution add a little Zn and a piece of 
platinum-foil. The antimony and tin will both be reduced to 
the metallic state, the Sb being deposited on the Pt as a 
brown or black coating. Presence of Sb may be confirmed 
by removing the Pt, washing carefully, treating with (NH4)2S and 
drying, when the coating will become Sb2S3, orange-red. 

To the solution to be tested for Sn add HCl enough to 
dissolve all the Zn which has been added, filter and test fil- 
trate with HgCls. (Page 17.) 

Dissolve the insoluble residue of Au and Pt (the residue 
will be dark-colored if either of these metals are present) in 
aqua regia and divide solution into two parts. 

Test one for gold with solution of FeS04, or a mixture of 
SnCl2 and SnCU. (Page 15.) 

Test the other for Pt by adding NH4CI, allow to stand 
overnight with addition of little alcohol, and precipitate of 
ammonium platinic chlorid will be obtained, yellow and crys- 
talline. (See Plate I, Fig. 1.) 

QUESTIONS ON GROUP II. 



Why is it necessary to wash the precipitate of Group II 
practically free from CI before dissolving in warm HNO3? 

How does the Hg found in Group II differ from the Hg in 
Group I? 

How does the Pb found in Group II differ from the Pb 
in Group I? 

Before making the final test for Sn, why is it necessary to 
dissolve all the Zn which has been added? 



20 QUALITATIVE ANALYSIS. 

In precipitating Group II why should the solution be made 
acid with HCl before adding H2S? 

AVhy is it better to use H2S gas rather than H2S water in 
precipitating metals of Group II? 

Before testing for Cd why add KCN to decolorize the copper 
solution? 



REACTIONS OF GROUP III. 

Iron, Fe (Ferrum). 

Atomic weight 55.9. Occurs widely distributed in nature 
combined with oxygen as Fe203 or Fe304; also as sulphid, FeS2^ 
and as carbonate, FeCOs. 

Iron forms two classes of salts, ferrous, represented by 
ferrous sulphate, FeS04; and ferric, represented by ferric sul- 
phate, Fe2 (804)3, or ferric chlorid, FeCl3. 

A solution for demonstrating the reactions of ferrous salts 
is best made by saturating cold dilute sulphuric acid with 
clean iron wire. A 3 to 5 per cent solution of fresh crystals 
of ferrous ammonium sulphate may be used. The ordinary 
ferrous sulphate or " copperas " is almost sure to contain some 
ferric salt. Use a 2 to 3 per cent solution of ferric chlorid 
and make the following tests, comparing the deportment of 
the ferrous and ferric solutions with each reagent. Write 
the reactions. 

H2S with pure ferrous salts gives no reaction; with ferric 
salts the iron is reduced to the ferrous combination, but gives 
no precipitate except sulphur. 

(NH4)2S gives with ferrous iron a black precipitate of FeS; 
with ferric it gives a precipitate containing FeS and S. 

NH4OH precipitates Fe'' as ferrous hydroxid, Fe(0H)2; 
color white if perfectly pure, but usually a dirty green from 
admixture of ferric compounds. The presence of NH4CI pre- 
vents a complete precipitation as Fe(0H)2. 



THE METALS. 21 

With ferric salts, NH4OH completely precipitates the iron 
as brick-red ferric hydroxid, Fe(0H)3. 

K4FeCy6 gives with ferrous salts a bluish-white precipitate 
of potassium ferrous ferrocyaiiide, K2FeFeCy6. 

With solution of ferric salts the deep Prussian blue, ferric 
ferrocyanide, Fe4(FeCy6)3, is thrown out. 

With potassium ferricyanid, ferrous salts give dark-blue 
precipitate of ferrous ferricyanid, Fe3(FeCy6)2. With ferric 
salts no precipitation occurs, but the color may change to 
green or brown. 

KCyS or NH4CyS gives no reaction with pure ferrous salts, 
but with ferric salts a deep red solution of ferric thiocyanate, 
Fe(CyS)3, is produced. This red color is destroyed by addi- 
tion of HgCl2, not affected by HCl, and may be extracted 
from aqueous solution by shaking with ether in which the 
Fe(CyS)3 is soluble. 

Aluminum, A1. 

Atomic weight 27.1. Aluminum constitutes a consider- 
able part of the earth's crust as a constituent of clay, feldspar, 
mica, etc. 

Its most important soluble salts are ammonia alum, 
NH4Al(S04)2l2H20, potash alum, KAl(S04)2l2H20, and alu- 
minum sulphate, Al2(S04)3. Use a 5% solution of either of 
these for the following tests: 

AI2 (804)3 with (NH4)2S and H2O gives a white precipi- 
tate of A1(0H)3. Write the reaction. 

A1(0H)3 is Hkewise produced by NH4OH, Na2C03, or 
NaOH; the precipitate is soluble in excess of fixed alkali 
hydroxids with formation of aluminates: 

A1(0H)3 + KOH = KAIO2 + 2H2O. 

The alkahne aluminates may also be formed by fusion 
with Na2C03 and KNO3 and then may be dissolved in hot 
w^ater. 



22 QUALITATIVE ANALYSIS. 

From the solution of KAIO2 the Al may be precipitated 
as A1(0H)3 by excess of NH4CI (difference from Zn, page 27). 

The presence of organic acids, tartaric, oxahc, etc., inter- 
feres with the precipitation of aluminium hydroxid and may 
entirely prevent it. The presence of ammonium chlorid favors 
its precipitation. 

Chromium, Cr. 

Atomic weight 52.1. Occurs as chrome iron ore or chromite, 
FeOCr203. Chromium forms two oxids, one basic, Cr203, 
the basis of chromic salts, as Cr2(S04)3, Cr2Cl6(CrCl3),* etc.; 
the other, CrOs, is an acid anhydride, crystallizes as dark-red 
needles, and gives rise to two series of salts: neutral chro- 
ma tes, such as K2Cr04, and acid chroma tes or dichromates, 
K2Cr207. 

The soluble chromic salts most easily obtained are chrome 
alum, KCr (804)2, chromic sulphate, Cr2(S04)3, and chromic 
chlorid, CrCl3. With a 5% solution of either of these the fol- 
lowing may be demonstrated: 

Cr2(SO)3 with (NH4)2S gives greenish precipitate of Cr(0H)3» 

Similarly to Al the chromium hydroxid is precipitated by 
NH4OH, alkahne carbonates or hydroxids; and then by boil- 
ing the Cr(0H)3 with NaOH or KOH, or by fusing with Na2C0a 
and KNO3, chromates of the alkalis are produced. 

The solid dichromate K2Cr207 with strong H2SO4 gives, 
in the presence of chlorids, the reddish-brown gas Cr02Cl2 
(chlorochromic anhydride or chromium dioxychlorid) used 
as a test for chlorids. (Page 46.) 

Analysis of Group III. 

(Fe, Al, Cr. Phosphates and oxalates being absent.) 

The filtrate from Group II must be freed from H2S by 
boiling with a few drops of HNO3 in a porcelain dish till a 

* There is a series of chromous salts, CrClg, Cr(0H)2, etc., corresponding to 
a chromous oxid, CrO, but the oxid itself is not known. 



THE METALS, 



23 



drop removed by a glass rod does not blacken filter-paper 
wet with solution of lead acetate. This treatment also serves 
to oxidize the iron (reduced by H2S) to ferric salt and at the 
same time concentrates the solution. To the clear solution thus 
obtained add 10 c.c. of NH4CI solution, then NH4OH till alka- 
line, when the metals of this group will separate out as hy- 
droxids: Fe(0H)3 brick-red, A1(0H)3 white, Cr(0H)3 bluish 
green. Filter, wash carefully and dry precipitates, removing 
paper from funnel. 



Group III. 




Groups IV, V, and VI. 



Scrape dried precipitate from paper in 
a crucible and cover well with a mixture 
of dry Na2C03 and KNO3 and fuse, keep- 
ing fusion liquid for at least three minutes. 
Cool. Boil the fused mass with H2O: filter. 



Al and Cr. 



Iron will remain on the paper ; Al and Cr will be in solution 
as alkaline aluminate and chromate. 

Divide filtrate (Al and Cr) into two parts. Test one por- 
tion for Al, by acidifying with HCl, adding (NH4)2C03 till 
alkaline and boiling, when Al will separate as a white floccu- 
lent precipitate of Al2(0H)6. 



24 QUALITATIVE ANALYSIS. 

Test second portion of filtrate for Cr by acidifying strongly 
with acetic acid, boiling to expel CO2 and adding a few drops 
of a solution of lead acetate. A yellow precipitate (PbCr04) 
indicates Cr. 

Wash the precipitate remaining on the paper (Fe) and 
dissolve in dilute HCl. Divide resulting solution (FeCls) 
into two parts and confirm presence of Fe by testing one with 
K4FeCy6 (blue precipitate) and the other with KCyS (red 
solution) . 

If iron is found, determine in original substance whether 
ferrous or ferric, by use of tests described on pages 20 and 21. 

QUESTIONS ON GROUP III. 

Why boil off H2S before precipitating the group with NH4OH? 

AVhy add HNO3? 

Of what use is the nitrate of potash (KNO3) in the fusion 
of the hydroxids of Al and Cr? 

In making the final test for Cr why is it necessary to add 
acetic acid, and why boil off the CO2? 

Why must HCl be added before making the final test for 
Al with (NH4)2C03? 

REACTIONS OF GROUP IV. 

Cobalt, Co. 

Atomic weight 59.0. Use a 2% solution of nitrate. Crys- 
talline salts of Co are usually of pink color; anhydrous salts 
are blue. 

Co(N03)2 with (NH4)2S gives precipitate of CoS, black. 
Test solubility of this precipitate in HCl. 

Make a borax bead by fusing a little borax in the looped 
end of a clean platinum wire. When a bead of clear " borax 
glass "has been obtained dip it in a little of the CoS just formed, 
and fuse again. The color of the bead when cold is a deep 
blue. 

Note. — Be sure and make the fusion complete; the use of an insufficient 



THE METALS. 25 

amount of heat will acount for much of the trouble experienced by students in 
obtaining satisfactory bead tests. 

Co(N03)2 with KNO2 forms a double nitrite, Co(N02)22KN02, 
soluble in water; but if acetic acid is added to strong acid 
reaction, the solution heated and then allowed to stand over- 
night, the Co is completely precipitated as another double 
salt, Co(N02)3,3KN02, yellow and crystalline. 

Nickel, Ni. 

Atomic weight 58.7. Occurs associated with Co, some- 
times with Fe as sulphid. 

Use a 2% solution of the sulphate or nitrate. NiS04 with 
(NH4)2S gives NiS, black. Test solubility in HCl. 

The borax-bead test applied to NiS or other nickel salt 
gives a bead yellowish brown when cold, but the color is easily 
masked by other metals. 

Ni salts with KNO2 give the soluble double nitrite of 
similar composition to the Co salt, Ni(N02)2,2KN02. The 
nickel salt, unlike the cobalt, is not easily decomposed, and 
is not precipitated by heating with acetic acid. Advantage 
is taken of this fact in effecting the separation of cobalt from 
nickel. (Page 27.) 

Manganese, Mn. 

Atomic weight 55.0. Occurs chiefly as the dioxid, Mn02, 
pyrolusite. 

Manganese salts are usually flesh-colored. The sulphate is 
easily obtained. A 3% solution may be used. 

MnS04 with (NH4)2S gives flesh-colored precipitate of ]\InS. 

Test solubihty in HCl. With a little of the precipitated MnS 
make a red-lead test for Mn as follows: 

Place in a test-tube a little red lead (Pb304). Add three 
or four cubic centimeters of nitric acid (about one part con- 
centrated HNO3 and one of H2O), and boil well. Add, by 
means of a glass rod, a little of the washed MnS to the mix- 
ture in the tube and boil again. Now dilute with water till 



26 QUALITATIVE ANALYSIS. 

tube is about three-quarters full, and allow to stand till liquid 
is clear. If Mn was present, the supernatant fluid will be a 
pink to red color due to the formation of permanganic acid, 
HMn04. 

Note.—BC\ or chlorids, even in small quantities, interfere with the reaction;, 
hence it is recommended to make the test on the sulphid. Reducing agents must 
likewise be absent. When these precautions are observed the test is a very- 
simple and extremely delicate one. 

MnS04 with NaOH gives flesh-colored Mn(0H)2 insoluble 
in excess of reagent (separation from Zn). 

Upon fusion with a mixture of KNO3 and Na2C03 man- 
ganese salts produce green manganates, as Na2Mn04. 

Zinc, Zn. 

Atomic weight 65.4. Occurs chiefly as the carbonate 
ZnCOs, calamine. A native carbonate of zinc is also known 
as smithsonite. The sulphid, ZnS (zinc blend), and the siH- 
cate are also natural sources of the metal. 

The sulphate, ZnS04, also known as white vitriol, is per- 
haps the most common salt. The chlorid is a constituent 
of many commercial liquid disinfectants and antiseptics. 
The nitrate also is easily obtained. 

A 2 or 3 per cent solution of any of these soluble salts- 
may be used in the following tests: 

ZnS04 with (NH4)2S gives a white precipitate of ZnS. 

Sulphid of zinc is the only white sulphid formed in the 
course of analysis of ordinary solutions, but the following 
white precipitates are formed: Sulphid of manganese is flesh- 
colored or dirty white. Aluminum hydroxid resembles sul- 
phid of zinc in appearance and is precipitated by (NH4)2S. 
Yellow (NH4)2S added to an acid solution will precipitate 
sulphur, white, very fine and difficult to filter out. 

ZnS04 with NaOH (or KOH) gives a white gelatinous 
precipitate of zinc hydrate, Zn(0H)2, soluble in excess of the 
reagent as Na2Zn02 (sodium zincate). 



THE METALS. 27 

Note. — Colorless gelatinous precipitates in slight amounts may escape de- 
tection, as it sometimes takes careful observation to see them, especially if the 
laboratory light happens to be poor. 

Na2Zn02 with H2S or (NH4)2S gives precipitate of ZnS. 

From solution of Na2Zn02 the Zn may be precipitated as 
Zn(0H)2 by addition of NH4CI, but further addition of the 
NH4CI redissolves the precipitate (distinction from Al, page 22). 

ZnS04 with K4FeCy6 gives white precipitate of zinc ferro- 
cyanid (Zn2FeCy6) insoluble in NH4OH. 

Note. — The ferrocyanid and the sulphid are the only two zinc salts not soluble 
in NH,OH. (Prescott and Johnson, page 179.) 

Soluble zinc salts and oxalic acid give crystals of ZnC204 
which may be recognized under the microscope (Plate I, Fig. 2). 

Analysis of Group IV. 

(Co, Ni, Mn, Zn. ) 

(In the presence of phosphates, oxalates, borates, etc., 
examine this group by the scheme given on page 36.) 

To the clear filtrate from Group III add (NH4)2S. A 
precipitate may be NiS, CoS, MnS, and ZnS. Wash the pre- 
cipitate and treat with cold dilute HCl which will dissolve MnS 
and ZnS only. 



CoS and NiS, black. 




Make a borax-bead test (page 24) of the precipitants. If 
a clear red-brown bead is obtained, Ni alone is present. If 
the bead is blue, Co is present, Ni may or may not be. 

Separation of Cobalt and Nickel. 

If Co is present, dissolve the black precipitate ofT the paper 
with aqua regia, evaporate in porcelain capsule practically 



28 QUALITATIVE ANALYSIS. 

to dryness, dissolve in H2O, add excess of acetic acid and 
potassium nitrite (KNO2). Allow to stand over night, when 
Co will separate out as a yellow crystalhne precipitate (page 25). 
Filter and test filtrate for Ni with NaOH, which gives a 
pale-green precipitate of Ni(0H)2 insoluble in excess of the 
precipitant. 

Separation of Manganese and Zinc. 

Boil the HCl solution of Zn and Mn to expel the H2S, then 
add a decided excess of KOH or NaOH and allow to stand 
ten minutes without heating. Mn will separate out as Mn(0H)2, 
while Zn will remain in solution as K2Zn02. 



Mn(OH),. 




Test precipitate with HNO3 and Pb304. (Red-lead test 
for Mn, page 25.) Test filtrate for Zn by adding H2S or a 
few drops of (NH4)2S, which will precipitate ZnS, white. 

QUESTIONS ON GROUP IV. 

Why dissolve the MnS and ZnS in cold and dilute HCl? 

Why is it necessary to separate all the Mn before testing 
for Zn? 

If traces of Co or Ni are dissolved by the HCl, how does it 
affect the final test for Zn? 

In this analysis (in absence of phosphates, etc.) what 
important difference between the behavior of salts of Zn and Al? 

Why is it necessary to allow time for complete precipitation 
of Co with KNO2? 

Why expel H2S before separating Mn? 

Where does this H2S come from? 



THE METALS. 29 



REACTIONS OF GROUP V. 

(THE ALKALINE EARTHS Ba, Sr, Ca, Mg.J 

Barium, Ba. 

Atomic weight 137.4. Occurs chiefly as the sulphate, 
BaS04, heavy spar, and BaCOa, witheritc. 

Use a 2% solution of the chloricl for tests. 

BaCl2 with (NH4)2C03 gives white precipitate of barium 
carbonate. Test solubility in acids. With soluble sulphates 
BaCU produces BaS04 insoluble in HCl. (Test for sulphates.) 

BaCU with K2Cr207 or K2Cr04 gives yellow precipitate of 
BaCr04. Barium salts moistened with HCl and held on a 
clean platinum wire give to the colorless flame of the Bunsen 
burner a green or yellowish-green color. 

Strontium, Sr. 

Atomic weight 87.6. Occurs as the carbonate, SrCOa, 
strontianite, also as the sulphate. 

Use a 3 to 4 per cent solution of the nitrate or chlorid for 
tests. 

Sr(N03)2 with (NH4)2C03 gives white precipitate of SrCOs. 

Sr(N03)2 with H2SO4 or soluble sulphate gives white pre- 
cipitate of SrS04, rather more soluble in water and more slowly 
formed than BaS04. 

A saturated solution of SrS04 may be used to test for 
barium in presence of Sr salts. 

Sr(N03)2 with K2Cr04 gives precipitate of SrCr04, but 
with the acid chromate (dichromate) of potassium, K2Cr207, 
no precipitate is formed except in concentrated solutions. 

Sr(N03)2 with oxaHc acid gives a precipitate of strontium 
oxalate, SrC204, crystallizing in the so-called envelop form 
(Plate I, Fig. 3). Salts of Sr color the Bunsen flame crimson. 



30 QUALITATIVE ANALYSIS. 

Calcium, Ca. 

Atomic weight 40.1. Calcium is widely distributed and 
very abundant, limestone, chalk, marble, and calc-spar being 
natural carbonates; CaCOs, gypsum, and alabaster are sulphates. 

Calcium phosphate occurs in the mineral apatite and is 
also a principal constituent of animal bones. 

Use a 3 or 4 per cent solution of CaCl2 for tests. 

CaCl2 with (NH4)2C03 gives white precipitate of CaCOs, 
easily soluble in acids. 

CaCl2 with oxalic acid or soluble oxalates gives a white 
precipitate of CaC204, similar in form to the SrC204 but much 
more difficult to obtain in the crystaUine condition. 

CaS04 is not precipitated except from moderately con- 
centrated solution. 

A saturated solution of CaS04 may be used to test for 
strontium salts in presence of Ca. 

Magnesium, Mg. 

Atomic weight 24.36. Principal sources are the carbonate, 
MgCOs, magnesite, and a double carbonate, CaMg(C03)2, dolo- 
mite. The sulphate MgS04 occurs in the mineral kieserite 
in the " Stassfurt deposit." " French chalk " (or talcum), 
soapstone, and meerschaum consist of magnesium silicate in 
varying states of purity. 

Soluble salts easily procured are the sulphate, MgS04, 
crystallized with seven molecules of water as Epsom salts; 
the chlorid, MgCU; and the nitrate, Mg(N03)2. A 5% solu- 
tion of either of these may be used in the following tests: 

Magnesium salts with (NH4)2C03 give a white precipi- 
tate of basic carbonate of variable composition. This pre- 
cipitate forms very slowly in dilute solution, and in the presence 
of NH4CI the formation of soluble double salts prevents the 
precipitation altogether. 

MgCl2 with Na2HP04 gives in fairly concentrated solution 



THE METALS. 31 

a white precipitate of MgHP04. In presence of NH4CI and 
NH4OH tlie alkaline phosphates precipitate iiiagnesium-ammo- 
niuin-phosphate, MgNH4P04,6H20, even from very dilute solu- 
tion (Plate I, Fig. 4). 

In case the precipitate has formed very slowly it may 
separate as small, almost transparent, crystals clinging to 
the sides of the beaker. 

Ammonium oxalate does not precipitate magnesium solu- 
tions. 

Analysis of Group V. 

(Ba, Sr, Ca, Mg.) 

To the filtrate from Group IV containing NH4CI and NH4OH, 
add (NH4)2C03. (If NH4CI and NH4OH are not present, add 
10 c.c. of NH4CI solution and NH4OH till strongly alkahne 
before proceeding with the analysis.) Ba, Sr, and Ca will be 
precipitated as carbonates; Mg will be held in solution by 
the anmionium chlorid. Filter. 



Ca, Ba, Sr, carbonates. 




Test the filtrate for Mg by adding Na2HP04, when a white 
crystaUine precipitate is NH4MgP04,6H20. 

To the carbonates on the paper add dilute acetic acid, 
which will dissolve the precipitate, forming acetates of. the 
three metals. 

Take a portion of the acetate solution in a test-tube and 
make a preliminary test for Ba by adding acid chromate of 
potassium (K2Cr207). A yellowish precipitate will be BaCr04. 

If Ba is present, add K2Cr207 to the whole of the solution 
and filter out the BaCr04. 



32 



QUALITATIVE ANALYSIS. 





Sr and Ca, acetates, KgCrgO;, etc. 



It is desirable to remove the excess of bichromate from 
the filtrate before testing for Ca and Sr * To do this add 
NH4OH till alkaline, then (NH4)2C03 will precipitate SrCOg 
and CaCOs. Filter and dissolve off the paper with acetic 
acid as before. 



CaCOg and SrCO^, which treated with acetic acid will give 



a solution of the acetates of Ca and Sr. 



Reserve about one-fourth of this acetate solution. To the 
remainder add dilute K2SO4 solution, which will precipitate 
SrS04. (If only shght amounts of Sr are present, it may take 
some time to complete the precipitation. If a large amount 
of Ca is present, some CaS04 may also be thrown down.) Filter. 



SrSO^. 



Ca(C2H302)2 or CaSO^. 



Test filtrate for Ca by adding ammonium oxalate, which 
will precipitate calcium oxalate, w^hite. 

* The object of removing the KJ^t^O^ is to furnish a colorless solution wherein 
the Sr or Ca precipitates may be more clearly discerned. It is not absolutely 
necessary and, in case the amount of Sr and Ca is probably slight, might be omitted 
as the operation is always attended with some loss. 




THE METALS. 33 

If there is any question about the precipitate thrown out 
by K2SO4 being Sr, make confirmatory test on reserved portion, 
either by flame test (page 29) or by adding CaS04 and allow- 
ing to stand twelve hours. CaS04 will precipitate Sr as SrS04, 
but of course cannot precipitate Ca. 

QUESTIONS ON GROUP V. 

Why add NH4CI before precipitating the group with 

(NH4)2C03? 

Why dissolve the precipitated carbonates in acetic acid 
rather than HCl? 

Why use the acid chromate of potassium (K2Cr207) in 
testing for Ba rather than the neutral chromate (K2Cr04)? 

Why precipitate Sr and Ca after separation of Ba with 
K2Cr207? 

REACTIONS OF GROUP VI. 

(THE ALKALI METALS, K, Na, NH^, Li. ) 

These bases are not precipitated by any group reagent 
and must be detected by individual tests. The following 
will be sufficient: 

Potassium, K (KaUum). 

Atomic weight 39.15. Occurs as carbonate in wood ashes, 
as nitrate in the " nitre beds " of India, etc., as chlorid from 
the Stassfurt deposit in Germany, as the mineral sylvite, also 
in the double chlorid of Mg and K (carnaUite). 

Nearly all potassium salts are soluble in water. The potas- 
sium platinic chlorid, K2PtCl6, the potassium acid tartrate, 
KHC4H4O6, and a few others are only sparingly soluble and 
may be precipitated by addition to the solution of an equal 
volume of alcohol, in which they are quite insoluble. 

The presence of potassium salts may be detected spec- 
troscopically or by the violet color given to the flame observed 
through blue glass. Make comparative tests with known 



34 QUALITATIVE ANALYSIS. 

solutions of sodium and potassium salts, using blue glass of 
sufficient thickness to obscure the yellow (Na) ray. 

Note. — la making the flame test the best results are obtained by evaporating a 
little of the original solution to dryness, moistening with HCl and then taking 
up on a loop of clean platinum wire. 

The platinic chlorid test may be made as follows: 
Add a few drops of HCl to a little of the solution, then 
evaporate to dryness. Keep at a low red heat till all ammo- 
nium salts have been driven off, cool, and take up in a little 
(not more than 5 c.c.) distilled water. Add a few drops of 
H2PtCl6 and about 5 c.c. of alcohol. Set aside for some time. 
K2PtCl6, yellow, will crystalhze out recognizable under 
the microscope. (Plate I, Fig. 5.) 

Sodium, Na (Natrium). 

Atomic weight 23.05. Occurs principally as chlorid in 
sea-water and in mineral deposits, and to lesser extent as nitrate. 
Chin saltpeter, and as cryoUte, the double fiuorid of Al and 
Na, (Na2AlF6), found in Greenland. 

Na may be detected by use of the spectroscope or by the 
persistence of the yellow flame obtained with a clean platinum 
wire and a colorless Bunsen flame. Make comparative test 
with small amount of known sodium salt. 

Sodium salts are soluble with only a very few exceptions. 
The pyroantimonate Na2H2Sb207 may be precipitated in the 
cold by a freshly prepared solution of potassium pyroanti- 
monate. (Prescott and Johnson, 228.) 

From solution stronger than 3% and nearly neutral, the 
double acetate of uranyl and sodium (NaC2H302, U02(C2H302)2) 
may be precipitated. (Plate I, Fig. 6.) As triple crystalline 
acetates may also be formed with Mg, Cu, Fe, Ni, and Co, 
it is recommended to first precipitate the bases of the first five 
groups, drive off ammonium salts, etc., as in the test for 
K with HaPtCle * 

* Behrens's Manual of Microchemical Analysis, page 32. 



THE METALS. 35 

Lithium, Li. 

Atomic weight 7.03. The carbonate and chloric! are used 
in pharmacy as uric acid solvents. 

The presence of lithium salts is easily shown after the pre- 
cipitation of strontium by the intense carmine color given 
to the Bunsen flame. 

The spectroscope furnishes a very delicate and positive 
test for this clement. 

Ammonium, NH4. 

Ammonium salts are generally soluble. H2PtCl6 precipi- 
tates the double chloride (NH4)2PtCl6, similar in appearance 
and crystalline form to the corresponding potassium salt. 
(Plate I, Fig. L) 

Ammonium salts are most easily detected by the evolu- 
tion of ammonia gas (NH3) whenever they are heated with 
fixed alkah, NaOH or KOH. 

The test may be made upon the original solution by boil- 
ing in a test-tube with a little 10% NaOH, and the escaping 
NH3 may be detected by the odor or, better, by suspending 
in the upper part of the tube a piece of moistened red htmus 
paper,* which is promptly turned blue by the " volatile alkah." 
The litmus-paper test is more dehcate than the odor test. Care 
should be taken that the paper does not touch the sides of 
the tube, as it may come in contact with traces of NaOH. 

Many ammonium solutions give off NH3 gas without the 
aid of any fixed alkali. Common examples are the carbonate, 
acid carbonate, hydrate, sulphid, and sulphydrate. 

* Blue paper may be reddened by leaving it a few hours in a wide-mouth 
bottle after wetting the under side of the stopper with a drop or two of acetic 
acid. 



36 QUALITATIVE ANALYSIS, 

Analysis of Groups III, IV, and V. 

When phosphates, borates, or oxalates are present. 

To the filtrate from Group II add NH4CI and NH4OH in 
slight excess. Heat to boiling and add (NH4)2S slowly (always 
keeping the solution at the boiUng-point) until precipitation 
is complete. Filter as rapidly as possible and wash with 
hot water, adding occasionally a little (NH4)2S. 

The filtrate, which may contain the barium and potassium 
groups, must be concentrated by evaporation, filtered if neces^ 
sary and set aside.* The precipitate may contain MnS, ZnS,. 
CoS, NiS, FeS, A1(0H)3, and Cr(0H)3 with phosphates or 
oxalates soluble in acids only. The color of the precipitate 
will give some indication of what is present. Test the pre^ 
cipitate for Mn by fusing a part with KNO3 and Na2C03. 

Treat the precipitate with cold dilute HCl in which CoS 
and NiS alone are insoluble. Filter. Treat insoluble residue 
for Co and Ni according to direction on page 27. 

The HCl solution, which may contain Mn, Zn, Fe, Cr, 
and Al as chlorids and phosphates and oxalates soluble in 
acids, and which is green or violet if much Cr is present, is 
boiled with a few drops of HNO3 until all the H2S is expelled. 

Test a small portion of the solution for Fe exactly as in 
analysis of Group III given on page 24. Of the remainder 
of the solution take about one-third, and add dilute H2SO4. 

A white precipitate may contain BaS04, SrS04, and pos- 
sibly CaS04. Filter, wash precipitate, and fuse with a mix- 
ture of Na2C03 and K2CO3. 

Note. — The mixture of the two carbonates in molecular proportions fuses- 
at a lower temperature than either salt alone. 

Filter and wash the carbonates thus formed, dissolve them 
in acetic acid and examine this solution for Ba, Sr, and Ca 

* If Xi is present, the filtrate is frequently brown or black, since NiS is some- 
"what soluble in an excess of (NHjgS, especially if much NH^OH is present. Tha 
NiS may be precipitated, after evaporation, by acidifying with HCl. 



THE METALS. 37 

as directed under the Ba group. To the filtrate from the 
precipitate produced by H2SO4, or to the solution in which 
112^04 has failed to give a precipitate, add three times its 
volume of alcohol; Ca if present is precipitated as white CaS04, 
and its presence may be confirmed by dissolving the pre- 
cipitate in water and adding (NH4)2C204, which precipitates 
CaC204, white. 

To the rest of the HCl solution add ferric chlorid carefully 
till a drop of the solution gives, when mixed with a drop of 
amnionic hydrate, a yellowish precipitate. To the solution 
add Na2C03 or K2CO3 till the acid is nearly neutralized, then 
add excess of freshly precipitated BaCOs, and allow to stand 
overnight. Filter. 



Cr and Al as hydrates. (Fe as phosphate or hydrate and 
BaCOa. ) 

MnClj, ZnClg, and possibly members of Group V. 



Transfer the precipitate to a small beaker and boil for 
some time wath NaOH or KOH. The Al will be converted 
into the aluminate KAIO2. The phosphate will be more or less 
completely changed to potassium or sodium phosphate. Filter. 



Cr(0H)3, BaC03, etc. 





KAIO2 and Na^HPO,. 



Test precipitate for Cr as on page 24. Add HNO3 to fil- 
trate till acid, then divide into two parts; test one for P2O5 
with (NH4)2Mo04. 

Test the other for Al by adding NH4OH till alkaline, when 
precipitate will be AIPO4, insoluble in acetic acid. 



38 



QUALITATIVE ANALYSIS. 



To the solution of Mn and Zn chlorids add a little HCl 
and boil. Then make alkaline with NH4OH, add (NH4)2S, 
warm sUghtly and filter. The precipitate (MnS and ZnS) 
may be dissolved in cold dilute HCl and tested for Mn and 
Zn as in analysis of Group IV, page 28. 

OUTLINE SCHEME FOR ANALYSIS OF GROUP L 

To about one-third of a test-tubeful of the unknown solution add a few 
drops of HCl. 

Ppt.- AgCl, HgCl, PbCl2. Add hot H„0. 



Residue^ AgCl, HgCl. 
Add NH.OH. 



Residue= HgCl. 
Test, page 6. 



Solution= AgCl. 
Test with HNO3. 



Test as on page 5. 



OUTLINE SCHEME FOR ANALYSIS OF GROUP IL 

To the warmed filtrate from Group I add HgS. A ppt. may be sulphids of 
As, Sb, Sn, Au, Pt, Cu, Cd, Bi, Hg, and Pb. 
Filter and treat with warm (NH^IgS. 



Residue is Group II (a), page 17, and 
consists of sulphid of Cu, Cd, Bi, Hg, 
and Pb. 

Treat on paper c warm dil. HNO3. 



Residue 

isHg. 

Dissolve 

in aqua 

regia and 

test c 

SnClj 

(page 17) 



Solution Cu, Cd, Bi, and Pb. 
Add H2SO4 and filter. 



Ppt. 

is 

PbSO, 



Solution is Cu, Cd, and 
Bi. 

filter." 



Ppt. is 
Bi(0H)3 



Solution is Cu and 
Cd. 



Test for 
Cu c HA 

and 
K^FeC.Ve 



Test for 
CdcKCN 
and H,S 



(page 18). 



Solution= As, Sb, Sn, Au, and Pt. Re- 
precipitate c HCl, filter and treat ppt. 
strong (NH4)2C03 sol. 



Residue^ Sb, Sn, Au, and Pt, 

sulphids. Treat c cone. HCl, 

dilute and filter. 



Residue 

Au and Pt. Dis 

solve in aqua re 

gia and divide. 



Pt. I. 

Test ior 

Au c 

FeSO, 

(p. 19). 



Pt. II. 

Test foi 

Pt c 

NH.Cl 

and alco- 
hol. 



Solution. 
Sb and Sn 
Tes^ for 
Sb cPt 
foil and 
Zn. 



Test for 
Sn in fil- 
trate c 

HgCl^ 
(page 19). 



Solution 

As. 

Make 

Gutzeit's 

or Fleit- 

mann's 

test for As 

(page 10) 



THE METALS. 



39 



OUTLINE SCHEME FOR ANALYSIS OF GROUPS III AND IV. 

Take the clear solution iti which HgS fails to produce a precipitate and boi 
with a few drops of HNO3 till HjS is expelled. Add NH,C1 and NH,OH. Filter 



Precij>itate=Gvo\x^ III. 
Cr. Fuse c NajCOg 



Fe, Al, and 
and KNO3. 



Residue = 

Fe. Test for 

Fe c KCyS 

and 

K.FeCye 

(page 24). 



Solutions =i^vo\i\)^ IV, V, and VI. Add 
(NHjjS and precipitate. Group IV— Co, 
Ni, Mn, and Zn. Treat with cold 
dilute HCl. 



Solution = k\ and Cr. 'Jiesidue= Co 



Divide solution and 



test for Al 
with HCl 

and 
(NHJ2CO3 
(page 23). 



test for Cr 
with acetic rate 
and lead ace- 
tate (page 
24). 



and Ni. Make 

borax- bead 

test. Sepa- 

Co by 

means of 

KNO2 (page 

27). 



Solution^ Mn and Zn. Boil 
and treat c KOH or 
NaOH. 



Precipitate = 
Mn(0H)2. 
Make red- lead 
test for Mn 
(page 25). 



Solution = 
KoZnOj. Test 
for Zn c H2S 

or (NHJ^S 
(page 28). 



OUTLINE SCHEME FOR ANALYSIS OF GROUPS III, IV, AND V. 

(Phosphates, oxalates, borates, etc., being present.) 
To filtrate from Group II add NH^Cl and NH^H. Heat and add (NHJjS. 
Filter rapidly. 



Precipitate^UnS, ZnS, CoS, NiS, FeS, A1(0H)3, Cr(0H)3, also phos- 
phates, etc., soluble in acids only. Fuse part of precipitate and 
test for Mn (page 28). Treat remainder c cold dilute HCl. 



Residue = 
CoS and 
NiS. Make 
borax- bead 
test and 
separate Co 
i f neces- 
sary, c 

KNO2 
(page 27). 



Solution =Mn, Zn, Cr, and Al. Divide solution into 
three parts of about 1/8, 2/8, and 5/8, respectively, 
and treat as follows: 



Filtrate, 
members of 
Ba and K 

groups. 



I 

Test 
small 
portion 
for Fe 
(page 

24). 



II 



To second portion add 
dilute H2SO,. 



Precipitate 
may be 
BaSO^, 
SrSO, or 
CaSO,. Fil- 
ter, wash, 

fuse c" 
Na^COs and 
K2CO3. Dis- 
solve f\ision 
in HA and 
analyze for 
Group V 



Solution = 

CaSO,. 
Add alco- 
hol; if pre- 
cipitate oc- 
curs, filter, 
dissolve in 
H2O, and 
test with 
ammonium 
oxalate. 



Ill 
To third portion add FeClg to 
combine c H3PO4, etc., then add 
NajCOg or KjCOg, and BaC03 

(page 37). 



Precipitate= Cr, Al, Fe, 
and BaCO^ Boil 
precipitate iJ NaOH 
and filter. 



Residue = 
Cr, BaCOs, 

etc. Test 
for Cr as on 

page 24. 



Solution 

KAIO2 

Test for Al 

as on page 

23. 



Solution = 

Mn and Zn 

Reprecipi- 

tate Mn 

and Zn as 

sulphids, 

and test 

according 

to page 26, 



40 



QUALITATIVE ANALYSIS. 



OUTLINE SCHEME FOR ANALYSIS OF GROUPS V AND VL 

To the clear filtrate from Group IV add (NHJ2CO3. 



Precipitate= Ba, Sr, and Ca. 
necessary to precipitate Ba. 



Add KgCrgO, if 



Precipitate= BaCrO^. 



Solution=ST and Ca. Re- 
precipitate Sr or Ca with 
(NHJ2CO3 and test, or 
CaSO^. Remove Sr with 
K2SO4 and alcohol, and 
test filtrate for Ca with 
(NHJAO4 (page 32). 



Solution==M.g and Group VI. 
Test for Mg with NaaHPO^ 
(page 31 ). Make separate 
tests for metals of Group 
VI according to pages 33, 
34, and 35 of the text. 



SECTION II.— ANALYTICAL REACTIONS OF THE ACIDS. 

In the analytical processes thus far described we have 
considered only the separation and detection of the basic 
or metallic part of the salt, that is, we have analyzed a solu- 
tion of ferric chlorid and found iron simply. It is necessary 
to find the chlorin. Before making any examination for acid, 
it will be possible to save a considerable amount of both time 
and labor by first carefully considering what acids are capable 
of forming soluble salts with the bases which have already been 
detected. To facilitate this consideration a table of solubilities 
will be found on the following page, by a careful study of which 
it will be possible to select such acids as are most likely to 
be present in the unknown solution under investigation, and 
also to neglect a number of acids which, from the solubility 
of their salts, together with the character of the solution (acid, 
alkaline, neutral and aqueous, or otherwise), will necessarily be 
absent. 

In this connection it is well to remember that practically 
all nitrates and chlorates are soluble in water; sulphates are 
mostly soluble, except those of barium, strontium, and cal- 
cium. Phosphates (di- or trimetallic), silicates, oxalates, and 
borates are practically insoluble, except those of the alkaline 



ANALYTICAL REACTIONS OF THE ACIDS. 



41 



TABLE SHOWING THE SOLUBILITY OF SALTS. 



Acetate 

Arseniate 

Arsenite 

Borate 

Bromid 

Carbonate 

Chlorate 

Chloric! 

Chromate 

Cyanic! 

lodid 

Nitrate 

Oxalate 

Oxid 

Phosphate 

Silicate 

Sulphate 

Sulphid 

Sulphocyanate.. 
Tartrate 



K 


Na 


NH, 


Mg 


Ba 


Sr 


Ca 

w 


Mn 

w 


Zn 

w 


Co 

w 


Ni 
w 


Fe 

w 


w 


w 


w 


w 


w 


w 


w 


w 


\v 


a 


a 


a 




a 


a 


a 


a 


a 


w 


w 


w 


a 


wa 


wa 




a 




a 


a 


a 


w 


w 


w 


\va 


a 


a 




a 


a 


a 


a 


a 


w 


w 


w 


w 


w 


w 




w 


w 


w 


w 


w 


w 


w 


w 


a 


a 


a 




a 


a 


a 


a 


a 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


\v 


w 


w 


w 


w 


w 


w 


w 


w 


w 


\\' 


w 


w 


w 


w 


w 


a 


wa 


wa 


w 


w 


a 


a 




w 


w 


w 


w 


wa 


w 


w 


a 


a 


ai 


ai 


ai 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


\v 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


\v 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 




a 


w 


w 


w 


a 


a 


a 


a 


a 


w 


vv 


w 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 




a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 


w 


w 


1 


1 


Wl 


w 


w 


w 


w 


w 


w 


w 


w 


wa 


w 


w 


w 


a 


a 


a 


a 


a 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


wa 


a 


a 


a 


wa 


a 


w 


a 


wa 



Fe, 



Acetate 

Arseniate 

Arsenite 

Borate 

Broraid 

Carbonate. . . . 

Chlorate 

Chlorid 

Chromate 

Cvanid 

lodid 

Nitrate 

Oxalate 

Oxid 

Phosphate. . . . 

Silicate 

Sulphate 

Sulphid 

Sulphocyanate 
Tartrate 



Or, 


AU 


Sb 


Sn" 


Sn»^ 


Au 


Ag 


Hg. 


Hg 


Pb 


Bi 


Cu 


w 


w 


w 


w 


w 




wa 


wa 


w 


w 


w 


w 


a 


a 


a 


a 


a 




a 


a 


a 


a 


a 


a 






a 


a 


a 




a 


a 


a 


a 




a 


a 


a 




a 






a 






a 


a 


a 


w 


w 


wa 


w 


w 


w 


1 


ai 


wa 


Wl 


wa 


w 














a 


a 


a 


a 


a 


a 


w 


w 




w 






w 


w 


w 


w 


w 


w 


w&i 


w 


wa 


w 


w 


w 


1 


ai 


w 


Wl 


wa 


w 


a 




a 


a 






a 


a 


wa 


ai 


a 


w 


a 










w 


' 




w 


a 


wa 


a 


w 


w 


wa 


w 


w 


a 


1 


a 


a 


wa 


a 


a 


w 


w 




a 


a 




w 


w 


w 


w 


a 


w 


w 


a 


a 


a 


w 




a 


a 


a 


a 


a 


a 


a&i 


a&i 


a 


a 


a& i 




a 


a 


a 


a 


a 


a 


a 


a 


a 


a 


a 




a 


a 


a 


a 


a 


a 


a 


ai 
















a 




a 


w&a 


w 


a 


w 


w 




wa 


wa 


wa 


1 


a 


w 






a 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 








w 




i 


a 


w 


a 




a 


w 


w 


w 


wa 






a 


a 


a 


a 


a 


wa 



Cd 

w 



w 

a 

a 

a 

a 

w 

a 

wa 
wa 



w, soluble in water; a, insoluble in water, soluble in acids; i, insoluble in 
water or acids; wa, sparingly soluble in water, readily soluble in acids; wi, spar- 
ingly soluble in water and acids; ai, sparingly soluble in acids only. 



42 QUALITATIVE ANALYSIS. 

metals. This latter statement is also true of carbonates, except 
that some of the carbonates will dissolve to appreciable extent 
in water containing CO2. Chlorids, bromids, and iodids are 
nearly all soluble except those of the first-group metals. Sul- 
phids are insoluble except those of Groups V and VI. Acid 
salts are usuall}^ more soluble than neutral salts. 

In making qualitative tests for the acids it is not necessary 
to separate them one from the other, as it is in case of the 
metals; hence the tests are individual ones, usually made upon 
the original substance or solution, and often require confir- 
mation before conclusive evidence is obtained. The grouping 
is therefore simply for convenience, as it thus becomes pos- 
sible to exclude a considerable number of acids by a single 
general test. 

Group I. may include such acids as give effervescence when 
their dry salts are treated with dilute H2SO4, as H2CO3, H2S, 
H2S2O3, H2SO3, HCN. 

Group II may include acids giving a precipitate with AgNOs 
in dilute HNO3 solution, as HCl, HBr, HI, HCN, HCNS, HNO2, 
HCIO, H4FeCy6, H3FeCy6, H2S2O3, H2S, HPH2O2. 

This second group may be further subdivided into three 
parts according to the color of the precipitate obtained 
(page 45). 

Group III may include acids forming insoluble salts with 
BaCl or CaCU and not found in Groups I or II, or H2SO4, H2C2O4, 
H3PO4, H3BO3, H2Cr04, HsSiOs. 

Besides the acids found in these groups there are three 
others of common occurrence: nitric (nitrates), chloric (chlo- 
rates), and acetic (acetates). 

Detection of Acids of Group I. 

(Acids eServescing with dilute sulphuric acid. HjCOg, HgS, HgSOj, 
H2S2O3, HCN.) 

To a quarter test-tubeful of the unknown solution, or a 
little dry substance on a watch-glass, add dilute H2SO4. If 



ANALYTICAL REACTIONS OF THE ACIDS. 43 

solution is very dilute, concentrate it before making test, as a 
slight amount of gas might be absorbed by the water. Watch 
carefully for any escape of gas and note any odor which may 
be given off. 

Carbonates evolve CO2, odorless, but if passed into Hme- 
water or baryta-water will give white precipitate of CaCOa 
or BaCOs. 

Sulphids evolve H2S, odor of rotten eggs. Confirm by 
adding a little dilute H2SO4 to the suspected powder (or solu-' 
tion) in a test-tube and holding over the mouth of the tube 
a piece of filter-paper wet with a solution of lead acetate. The 
test-tube may be warmed slightly to expel the gas, when a 
dark-colored stain will appear on the filter-paper, due to the 
formation of PbS. 

Sulphites evolve SO2, odor of burning sulphur. Sulphites 
in neutral solution may be further identified by the deep-red 
color produced with ferric chlorid. The color is discharged 
upon addition of dilute acids, HCl, H2SO4 (difference from 
HCyS.) 

Thiosulphates also evolve SO2, but at the same time the 
mixture becomes cloudy from precipitation of sulphur.* 

Thiosulphates in neutral solution treated with ferric chlorid 
give a violet to purple color, fading (rapidly upon warming) 
to a colorless solution. In mixtures of sulphites and thio- 
sulphates both acids may often be detected by the use of FeCla, 
the deep-red coloration of the mixed acids rapidly fading 
to the lighter red of Fe2(S03)3 (not to colorless solution). 

Cyanids evolve HCN, odor of peach-stones. (Mercuric 
cyanid does not respond to this reaction.) Confirm by reac- 
tions given under Group II. 

* Sulphids may also precipitate sulphur in presence of compounds capable of 
oxidizing the HgS, such as FeCls. In the absence of sulphates either HgSOs or 
H2S2O3 can be oxidized to HgSO^ by heating with HNO3 and a precipitate of 
BaSO. obtained with BaCl^ 



44 QUALITA TIVE .ANALYSIS. 

Preliminary Tests for Common Acids of Groups II 

AND III. 

(In preparatory courses the acids given in this list may be sufficient. ) 

From the acids of Group II and III it may be desirable 
to select for laboratory practice, at least at the beginning 
of the acid work, the more common members of the groups. 
These will be HCl, HBr, HI, HCN, and H2S of Group II and 
H2SO4, H2C2O4, and H3PO4 of Group III; and tests for them 
may be made as follows: 

Chlorids give with AgNOs in presence of HNO3 a white 
curdy precipitate of AgCl, much more freely soluble in ammonia 
than any other acid of the group here given except the cyanid 
AgCN, but HCN is a member of the first acid group and would 
have been previously detected. 

Bromids with AgNOs and HNO3 give a precipitate of AgBr 
similar in appearance to AgCl, but with a slightly yellowish 
color and only sparingly soluble in NH4OH. 

The tests described on page 46 should also be made if 
bromids or iodids are suspected in the solution. 

Cyanids, see Group I. 

Sulphids will give a black precipitate with AgNOa, and 
have been previously considered in Group I. 

Sulphates may be detected by first acidifying the solution 
strongly with HCl (filtering out a precipitate if any occurs) 
and adding solution of BaCU; a white precipitate will then 
be BaS04, showing presence of sulphates in solution tested. 

Phosphates in a solution containing HNO3 and free or 
nearly free from HCl will give, with ammonium molybdate, 
a yellow crystalline precipitate of ammonium phosphomolyb- 
date. 

Oxalates may be detected, in a solution free from sul- 
phates and which is slightly acid with acetic acid, by simple 
addition of calcium chlorid, which will precipitate CaC204. 
white and crystaUine. 



ANALYTICAL REACTIONS OF THE ACIDS. 45 

Detection of Acids of Group II. 

(Giving precipitate with AgNOg in presence of dilute HNO3. ) 

To the solution to be tested add a very slight amount of 
HNO3 and a few cubic centimeters of AgNOa solution. A pre- 
cipitate indicates acids of this group. 

(a) The precipitate is white or nearly white, HCl, HBr 
(yellowish white), HI (yellow), HCN, HCNS, H4FeCy6 (slowly 
turns blue), HCIO,* and HNOs. (AgNOs is soluble in ILXOj 
unless quite dilute.) Test the solubility of the silver precipi- 
tate in ammonia-water after decanting the supernatant fluid 
and it will be found that AgCl, AgCN, AgN02, AgsFeCyg 
are freely soluble; AgCyS, AgBr, Ag4FeCy6 are slightly or 
slowly soluble; Agl is practically insoluble. 

(6) The precipitate is red-brown or orange, soluble in 
NH40H = H3FeCy6. 

(c) The precipitate is black or turns black upon warming : 
H2S (black immediately). HH2PO2 (starts to precipitate 
white, but rapidly turns black), H2S2O3 (precipitates white, 
turns black slowly or upon heating). 

Sulphids (H2S) and thiosulphates (H2S2O3) may also be 
detected as described under Group I, Acids. 

To distinguish between the ichite precipitates obtained 
with AgN03 shake a Httle of the solution with a few centi- 
meters of dilute indigo solution. The indigo is decolorized by 
hypochlorites (HCIO) and by nitrites (HNO2). 

Hypochlorites hberate I from KI without the addition of 
acid. 

Note. — Hypochlorite sohitions are usually quite strongly alkaline, and in 
such cases a considerable amount of iodid is necessary to obtain the character- 
istic color in chloroform or with starch. 

Nitrites liberate I from KI after the addition of acetic 
acid. They also give a brown coloration with acetic acid 

♦Precipitate is AgCl. Reaction is 3NaC10 + 3AgX03=2AgCl + Aga03+ 
SNaNOs. 



46 QUALITATIVE ANALYSIS. 

and a crystal of ferrous sulphate. (Nitrates require a stronger 
acid.) 

Note. — This test is much more dehcate than either of the others given, and 
if the solution is very dilute it is well to make it, even if the indigo color is not 
discharged. 

With a few drops of FeCls, sulphocyanates or thiocyanates 
(HCNS) give a deep blood-red solution. The color is soluble 
in ether and may be discharged by HgCl2. Ferrocyanids 
(H4FeCy6) give deep-blue precipitate. 

If the test given under Group I is not conclusive, cyanids 
may be converted into sulphocyanids by addition of a few 
drops of (NH4)2S and evaporation on the water-bath to dry- 
ness. It may be then dissolved in a Httle distilled H2O, fil- 
tered and tested with FeCls. 

lodids and bromids (HI and HBr) may be detected in 
the same solution by adding CI water, very cautiously at 
first, and shaking with chloroform. The CI liberates, first, 
the iodin, which is dissolved by the chloroform with violet color. 
Excess of CI decolorizes the iodin and liberates the bromin, 
which in turn is dissolved by the chloroform with yellow to 
red color. 

Chlorids (HCl) may be distinguished from HBr and HI 
by the ready solubihty of the silver precipitate in NH4OH. If 
bromids and iodids are present, hberate the halogens by means 
of Mn02 and H2SO4, pass the mixed gases into a solution of 
aniline in acetic acid (4 c.c. of saturated aqueous solution 
of aniline and 1 c.c. glacial acetic acid). Iodin gives no pre- 
cipitate, bromin gives a white one, chlorin a black one. (Pres- 
cott and Johnson, page 336.) 

This is a delicate and very satisfactory test for bromin, 
not so delicate for chlorin in the presence of bromids. For 
such cases the following chloro-chromic anhydride test is recom- 
mended. Neutralize the solution if necessary, evaporate to 
dryness, transfer residue to a test-tube of rather small diam- 
eter, add a Httle soHd K2Cr207, then concentrated H2SO4. 



ANALYTICAL REACTIONS OF THE ACIDS. 47 

Decant the jwnes into a wider test-tube containing a few cen- 
timeters of NH4OH. 

If the chlorochromic anhydride is evolved, ammonium 
chromote will be formed. Test by making acid with acetic 
acid, then adding acetate of lead. A yellow precipitate of 
lead chromate indicates chlorin in the original solution. 

Acid Group III. 

(Acids forming insoluble barium or calcium salts, not included in the 
Acid Group I or II.) 

The members of this group may be separated from each 
other, although this is not necessary unless several members 
are present. H2SO4, H2C2O4, H2Cr04, H2Si03, H3BO3, H3PO4, 
separated as follows: To a little of the unknown solution 
add 2 or 3 c.c. of HCl; a white or gelatinous precipitate which 
is not dissolved by dilution with water and warming is prob- 
ably silicic acid. Make a bead test with microcosmic salt; 
the particles of Si02 remain undisturbed by the hot bead, 
forming the so-called silicon " skeleton." Filter out the siUcic 
acid and add CaCl2 or a mixture of BaCl2 and CaCl2; a white 
precipitate will be BaS04 * (test for sulphates) . The Ba and 
Ca salts of all remaining acids of the group being soluble in HCL 

Filter out the BaS04, and to the filtrate add NH4OH, which 
will cause a precipitate of barium oxalate, chromate, borate, 
and phosphate. Filter, wash precipitate two or three times, 
reject wash-water, then transfer to test-tube by making a small 
hole in point of paper and forcibly washing through with the 
least possible amount of water; acidulate strongly with acetic 
acid, which will dissolve the phosphates and borates, leaving 
undissolved the oxalates (BaC204, white) and chromates 
(BaCr04, yellow.) 

* If the HCl is too strong, BaClg may be precipitated as such, but the pre. 
cipitate in this case will form more slowly than the BaSO^; it will have a crys- 
talline appearance and will dissolve upon addition of water. 



48 QUALITATIVE ANALYSIS. 




Oxalic and chromic acids as barium salts. 



Phosphoric and boric acids. 



Divide the filtrate into two parts, a and h. Test one 
part, a, for H3PO4 by adding to it an excess of ammonium 
molybdate in HNO3, when a yellow precipitate (forming some- 
times after several hours' standing) is ammonium phospho- 
molybdate (test for phosphates); the mixture may be warmed 
to hasten precipitation; the degree of heat should not exceed 
40° C, as the ammonium molybdate might be decomposed,, 
giving a yellow precipitate similar to the phosphomolybdate. 

Note. — If As is present, it must be removed by HgS before testing for H3PO4. 

Test the other part, h, for H3BO3 by evaporating to 
dryness in a porcelain dish; then moisten with strong H2SO4, 
cover with a Httle alcohol and ignite. Boric acid will give 
to the flame (particularly the edge) of the burning alcohol 
a green color due -to formation of ethyl borate. This color 
is more easily apparent if the dish is placed in a darkened 
corner. 

A test for H3BO3 may also be made with turmeric paper, 
which if dipped into a solution of boric acid, or of a borate 
mixed with HCl or H2SO4 to shght but distinct acid reaction, 
and dried at 100°, becomes red; the red color becomes bluish 
black or greenish black when moistened with a solution of an 
alkali or an alkaline carbonate. If there is a suspicion that 
H2Cr04 and H2C2O4 are both present, dissolve the precipitate 
of barium oxalate and chromate off the paper with dilute HCl; 
divide the filtrate into two parts and test one for H2Cr04 by 
addition of H2O2, which with chromates in presence of HCl 
produces a deep-blue solution and ultimately CrCls. 

In the absence of chromates, the precipitate being white^ 



ANALYTICAL REACTIONS OF THE ACIDS. 49 

oxalates may be confirmed by coloring the second part of 
solution faint pink with dilute solution of KMn04 and warm- 
ing, when the color will be discharged. 

In the presence of chromates (the precipitate being yellow) 
it will be necessary to test the original solution for oxalates 
as follows: To a few centimeters of the unknown add alcohol; 
warm. The chromate will be reduced to CrCls. Add NH4OH 
till alkaUne and filter out the precipitate, Cr(0H)3. The 
filtrate may be tested for oxalic acid as above, or with CaCl2; 
a white precipitate being CaC204. 

The remaining acids of importance not included in either 
of the three preceding groups are nitric, HNO3, chloric, HCIO3, 
and acetic, HC2H3O2. 

Nitrates. — Saturate 5 c.c. of a very dilute nitrate solution 
with FeS04. Filter and carefully underlay the clear filtrate 
with concentrated sulphuric acid; a dark ring (pale red-brown 
to nearly black) at point of contact of the two liquids shows 
presence of a nitrate. 

Chlorates. — A solution free from chlorids or hypochlorites 
treated with Zn and dilute H2SO4 will give a test for HCl if 
chlorates were originally present, the chlorate having been 
reduced by the nascent H: 

2KC103 + 6Zn + 7H2S04 = 6ZnS04 + K2S04 + 2HC1 + 6H2O. 
Boiling with sulphurous acid also reduces HCIO3 (and HCIO) 
to HCl. 

If the substance is in solid form, a very small particle may 
be warmed with concentrated H2SO4. Chlorates detonate 
and give off yellow fumes of CIO2: 

3KCIO3 + 2H2SO4 = 2KHSO4 + KCIQ4 + 2CIO2 + H2O. 

Acetates give with ferric chlorid a red color which is not 
discharged by HgCl2 (difference from sulphocyanate), but 
may be discharged by HCl (difference from sulphocyanate 
and meconate). 

A more positive test is the formation of the ethyl ester 



50 QUALITATIVE ANALYSIS. 

or acetic ether. A blank test for comparison should always 
be made, the method of procedure being as follows: 

Take two test-tubes of practically equal diameter, mix 
in each equal volumes of alcohol and strong H2SO4; warm 
the tubes together; then into one introduce a few centimeters 
of the unknown solution, and into the other an equal volume 
of H2O. Heat again to a boihng-point and compare the 
odors from the two tubes. The acetate is easily detected 
if present. 

SECTION III.— ANALYSIS IN THE DRY WAY. 

In the examination of solid substances much may be 
learned by a few simple tests directly applied to the sub- 
stance, which has been reduced (if necessary) to the form of 
a powder. 

Some of these are usually used as preliminary to the solu- 
tion of the substance and regular analysis in the wet way. 
These tests may be made quickly and, with a little elaboration, 
will often give all the information required regarding an unknown 
substance. 

The practical questions of actua experience are usually 
simple ones. It is not an analysis of an unknown solution 
possibly containing all the metals of one or more groups that 
interests an active practitioner, but a specific inquiry as to 
whether or no this or that preparation contains or does not 
contain the necessary or the undesirable ingredient, whether 
the thing is of the composition or of the strength represented, 
and a few minutes' work in the laboratory, especially if aided 
by the microscopical tests given in a subsequent chapter, will 
frequently be found sufficient to answer questions of this 
character. 

The tests made in the dry way are not as deHcate, nor 
are the results obtained (especially negative ones) as con- 
clusive, as those of a systematic analysis of the substance in 



ANALYSIS IN THE DRY WAY, 51 

solution, and in occasional cases it may be necessary to resort 
to the more tedious process. 

Before undertaking the analysis of a substance, note care- 
fully its physical properties of odor, color, and solubility; also 
whether it is magnetic, metallic, or crystalline. 

The volatile acids, certain ammonium compounds, bromin 
and iodin may be detected frequently by their odor. 

Colors of Salts and Solutions. 
The following colored salts are soluble in water: 

Black Silver albuminate (argyrol, etc. ) 

Violet or purple Chromic salts and permanganates 

Red CrOa and acid cliromates, KsFeCyg, sodium- 

nitro-prusside, HgPtClg 

Reddish brown or purple-red Manganic salts 

Reddish yellow Ferric salts and AuCla 

Yellow Neutral chromates of the alkalies, salts of 

uranium 

Pale yellow. K^FeCyg (Potassium ferrocyanide). 

Pink Salts of cobalt 

Pale pink Manganous salts 

Green Ferrous salts, nickel salts, certain copper 

salts 

Dark green Some chromic salts 

Blue-green Chromates 

Blue Cupric salts 

The following colored substances are insohihle in water: 

Black Carbon and carbids, metals, many metallic 

sulphids, oxids of Cu, Fe, Mn, and Pb. 
Iodin is bluish black 

Red HgO, HgS, Hgl^, PbaO,, As^Sg 

Brick-red Amorphous phosphorus, FcgOa 

Light brown PbO, litharge 

Yellow S, HgO, CdS, As^Sa, Pbl„ AggPO^, ammo- 
nium phospho-molybdate, and chromates 
of the heavy metals, PbCrO^, BaCrO^ 

Green Some copper compounds, CU2T2, Paris green, 

etc., Cr.Os 

Blue Some copper compounds, Prussian bhie, 

ultramarine; anhydrous salts of cobalt 



62 



QUALITATIVE ANALYSIS. 



METHODS OF EXAMINATION. 

Powder the substance and apply tests described in this 
chapter, which will be considered in the following order: 

A. Ignition on the platinum foil. 

B. Closed-tube test. 

C. Flame test on platinum wire. 

D. Examination with the blowpipe on plaster slab. 

E. Bead tests on platinum wire. 

F. Special tests, distinguishing or confirmatory. 



A. Ignition on Platinum Foil. 

A piece of platinum foil about 1 inch square is pressed 
into the palm of one hand with the thumb of the other in 
such a way as to leave the foil shghtly concave. 

The Bunsen flame is turned down to about J inch in 
height, the air-supply being so regulated that combustion 
is perfect. The platinum foil, holding a few grains of the 
unknown substance and held by crucible-tongs, is heated care- 
fully at first, and then the heat is gradually increased until 
no further apparent change takes place in the substance. 

The majority of phenomena occurring under A are more 
easily observed in the test made with the closed tube, B, 
and will be given under that head. There is, however, some 
information more easily obtained by use of the platinum. 

Observed Phenomena. Indication. 



The substance melts and steam is given off. 



The substance hums (a) at comparatively low 
temperature with blue flame and odor of SOg 
or burning matches. 

(6) With yellow flame and much smoke. 

(c) Blackens and then burns at fairly high tem- 
perature, leaving white or gray ash. 

{d) Blackens without burning. 



Water of crystallization^ 
NH4NO3 or H^C^O,, which 
entirely disappears. 



Sulphur. 

Fat, waxes, resins, etc. 

Carbonaceous matter other 

than fats, etc. 
Formation of oxids of Fe, Co, 

Ni, or Cu. 



ANALYSIS IN THE DRY WAY. 



53 



Observed Phenomena, 

Vapors are given off: 
(a) Of a violet color. 
{h) Of a red- brown color. 

(c) Of a greenish-yellow color. 

(d) White, practically odorless. 

(e) White with odor of NH3. 
(/) White with odor of garlic. 

(g) White and yellow with ammoniacal or 
empyreumatic odor. 
The substance decrepitates. 

Examine residue on foil; add a drop or two of 
water and test with litmus-paper. 
If found to be acid. 
If alkaline without blackening. 

If alkaline with blackening. 



Add a drop of dilute HCl, effervescence. 



Indication. 

lodin. 

Br or nitrogen oxids. 

Chlorin or ClOg. 

Some ammonium salts.NH^Cl, 

(NHj,SO„etc. 
Ammonium carbonate. 
Arsenic. 

Organic matter. 
Water held mechanically by 
crystals, as NaCl, etc. 



Acid salts. 

Fixed alkali hydrates or car- 
bonates. 

Carbonate formed by com- 
bustion of organic c o m - 
pounds. 

Carbonates. 



B. Closed-tube Test. 

Select a tube of soft glass about 5 or 6 inches in length. 
Seal one end and enlarge slightly. Into the bulb thus formed 
introduce a few grains of the unknown powdered substance. 
Heat carefully, making the following tests at various stages 
of the process. Note the odor of escaping gases. 

Test for oxygen by inserting a glowing spUnter into the 
tube. 

Test for combustible gases by occasionally applying flame 
to the open end of the tube. 

Bring to the mouth of the tube a clear drop of Ba(0H)2 
solution. If the drop becomes turbid, CO2 is indicated. 



Observed Phenomena. 

Steam condenses in cold part of tube. 
Oxygen is evolved. 



Carbon Dioxid is evolved. 



Indication. 

See under A. 

A peroxid, chlorate, some 
oxids (as HgO), alkali ni- 
trates. 

Carbonates, oxalates (at high 
temperature), organic 
matter. 



54 



QUALITATIVE ANALYSIS. 



Observed Phenomena. 

A Combustible Gas is formed: 

(a) Burning with a luminous flame, black 
residue remains in tube. 

(&) Burning with a blue flame, 
(c) Burning as in (b) and with odor of SOg. 
A Sublimate forms in the cooler part of the 

tube. Examine under microscope. 
Colorless with partial decomposition. 
Color is white with production of garlic odor, 

crystalline. 
Color is white when cold. Yellow when hot, 

crystalline. 
Color is white — it sublimes directly without 

melting and blackens with NH^OH. 
A white sublimate which by treatment with 

slaked lime yields NH3. 

A white subUmate of AsgOa with black residue 
in tube and odor of acetic acid. 

Sublimate is gray, consisting of small globules 
which can be made to unite by rubbing. 

Sublimate consists of reddish yellow to red 
globules, yellow when cold. 

Sublimate darker than above and reddish 
yellow when cold. 

Sublimate is brown to black "metallic mir- 
ror," soluble in NaClO. 

Ditto; dead black, insoluble in NaClO. 

Sublimate is black accompanied by violet 
vapor. 

Sublimate black, turning red when rubbed. 
No sublimate is formed, but the color changes 
to 

Yellow when hot, white when cold. 

Reddish brown when hot, yellow when cold. 

Black when hot, red when cold. 

Black when hot, brick-red when cold. 

Dark orange when hot, yellow when cold. 
Black residue without other visible manifesta- 
tion. 
Substance melts without a sublimate being 
formed. 



Indication. 



Hydrocarbons from organic 

matter. 
CO from oxalates. 
HgS from moist sulphids. 



Oxalic acid. Plate II, Fig. 1. 

AS2O3. Plate II, Fig. 2. 

HgCl2. Plate II, Fig. 3. 

HgCl. 

Ammonium salts. Plate II, 
Fig. 4. 

Paris green. 

Hg from HgO, amalgam, etc. 
Plate II, Fig. 5. 

Sulphur. 

Native Sulphid of arsenic. 

Metallic arsenic. 
Metallic antimony. 

lodin. Plate II, Fig. 6. 
HgS, cinnabar. 



ZnO. 

PbOorBigOg. (See D.J 

HgO (Hg sublimes). 

FCgOg. 

Chromates of Pb, etc. 

Oxids of Cu, Co, etc. (See 

A.) 
Salts of the alkaline metals. 



C. Flame Test with Platinum Wire. 

Introduce the substance on platinum wire into the edge 
of the flame. More satisfactory results are sometimes obtained 
if the solid is first moistened with HCl (page 34) . The flame 
is colored as follows: by Na, yellow; K, violet; Li, carmine; 



ANALYSIS IN THE DRY WAY. 



55 



Sr, crimson; Ca, orange-red; Ba, yellowish green; Cu, usually 
bright green; CUCI2, an intense blue; H3BO3, pale green; Sb, 
greenish blue; Pb, As, Bi, livid blue. 

D. Blowpipe Test on Plaster * 

Smooth plaster slabs about 1 inch wide and 4 inches long 
are well suited for these tests. These may be prepared by 
making a magma of calcined plaster and pouring upon a glass 
plate. Before it hardens mark deeply with a spatula into slabs 
of desired shape and, after it is throughly dried, break as 
marked. 

Make a little depression near one end of the slab and in it 
place a small amount of the substance to be tested; then if 
a fine oxidizing flame is made to play over the surface of the 
assay, characteristic coatings of oxid or sublimate may be 
obtained. 

In many cases the character of the substance may be deter- 
mined more easily by first moistening the assay with various 
reagents. Tetrachlorid of tin, cobalt nitrate, and " sulphur 
iodid " are the most valuable of the reagents so used. The 
^' sulphur iodid " is not of definite composition, but a mix- 
ture of about equal w^eights of sulphur and potassium iodid. 



D. I. Examination without Reagents. 



Observed Phenomena. 

Substance melts to bright metallic globules with 
brownish-yellow deposit near assay. Re- 
quires high heat. Assay revolves. 

Substance melts to bright globule with coating 
on plaster, deep orange when hot, light 
yellow when cold. 



Indication. 

Silver. 

Lead or bismuth (See D. II. ) 



* Substances sufficiently identified by previous tests have been omitted. This 
method will be found useful mainly in the identification of metals. 

The Author was greatly aided in the preparation of this list by Mr. Geo. F. S. 
Pearce of the Harvard Dental School, who carefully verified each test. 



56 



QUALITATIVE ANALYSIS. 



Observed Phenomena. 

Substance remains or becomes black without 
melting. No coating on plaster. 

Substance volatilizes with white fumes, but 

leaves dark stain; gray to black. 
Substance melts with white or gray oxid on 



Forms a white or gray oxid without fusion. Coat- 
ing on plaster is yellow over brownish black. 

Forms bulky white oxid mth active combustion 
of assay. 

Forms gray coating easily volatilized. 

Cherry-red — crimson to black according to 
amount of substance deposited. Odor of 
rotten horse-radish; coating not permanent. 

White coating or white fumes at very high heat. 
Assay burns with bluish- white light. 

Silver- white. Assay remains unchanged. 



Indication. 

Copper or iron. (See A; also 
F.) 

Antimony or arsenic. (See F. ) 

Tin. (SeeD. lU.) 

Cadmium. 

Magnesium. 

Mercury for amalgams. 
(SeeD. II.) 

Selenium. 

Zinc. (SeeD. III.} 
Platinum, metalhc. 



D. II. Cover substance with KI and S. Use oxidizing flame. 



Observed Phenomena. 

Dirty-white and hght-gray coating. Treated 
with fumes of strong NHg and again placed in 
oxidizing flame gives bright- red color. Me- 
talhc globule is dull and brittle. 

Dirty white half an inch from assay. Brown 
directly under assay. No change when 
treated as above with strong ammonia fumes. 
Metalhc globule is bright and malleable. 

No coating near assay. Lead- colored, one to 
one and a half inches, shading to yellow. 

Coating bright red when hot, fading to yellow 
when cold. 

Fine brown coating, very volatile. 



Indication. 



Bismuth. 

Lead. 

Mercury. 

Cadmium. 
Antimony. 



D. III. Examination with Solution of Cobalt Nitrate. 

Heat substance on plaster in the oxidizing flame, moisten 
well with cobalt nitrate, and again apply oxidizing flame. 



Observed Phenomena. 

Color is deep blue. 

Substance is infusible. 

Color is fine blue. Substance fusible. 

Color is yellowish green. 
Drab to bluish green. 



Indication. 

Aluminium. 

Infusible sihcates. (See F. ) 

Alkahne sihcate, borate, or 

phosphate. 
Zinc. 
Tin. 



ANALYSIS IN THE DRY WAY. 57 

D. IV. Examination with Tetrachlorid oj Tin. 

Observed Phenomena. 



Coating pale blue to lavendar. 
Coating fine blue, in places almost black. 
Delicate pink to red produced only by oxidizing 
flame. 



Indication. 

Bismuth. 
Antimony. 

Neutral and acid chromates. 



E. Bead Tests. 

The bead tests are made with borax, as described on page 24, 
or in a similar manner with microcosmic salt, NaNH4HP04, 
which by action of the heat gives up NH3 and H2O, becoming 
sodium metaphosphate, NaPOs. These substances fused on a 
loop of platinum wire unite with many of the metallic oxids, 
forming '' beads " of various characteristic colors, some of 
the more important given below. 

With Borax. 

Co in the oxidizing flame gives an intense blue bead. 

Ni gives a red-brown, yellow when cold. 

Cu '' a green, blue or bluish green when cold. 

Cr '' green. 

Fe '' a red, yellowish when cold. 

Mn '' an amethyst. 

With Microcosmic Salt. 

Cobalt, copper, nickel, and iron give colors similar to those 
obtained with borax. Manganese gives a violet bead when heated 
in the oxidizing flame, but a colorless one in the reducing flame. 

F. Special Tests Distinctive or Confirmatory. 

The oxids of copper and iron may be distinguished by 
adding a drop of HNO3, warming gently to drive off excess 
of acid (high heat will decompose the nitrate, giving the oxid 



58 QUALITATIVE ANALYSIS. 

again), and then adding a drop of solution of K4FeCy6. Fe: 
will give dark-blue coloration; Cu will give a brown. 

To distinguish between As and Sb stains, add a drop of 
hypochlorite solution (NaClO). The arsenic stain will dis- 
solve; the antimony stain will remain unaffected (see page 14). 

Antimony gives a very characteristic coating on plaster if 
treated with tetrachlorid of tin. The coating is bluish black 
near assay, fading away to a very delicate color at greater 
distance. It appears almost immediately and is permanent. 

In case of suspected silicates make the " silica skeleton '^ 
with a bead of microcosmic salt (page 47). 



PART 11. 

DENTAL METALLURGY, 

INCLUDING THE CHEMISTRY OF ALLOYS. AMALGAMS, SOLDERS, 
AND CEMENTS. 



SECTION I.— THE METALS. 

The metals occur in nature to quite an extent free, but 
more often combined with other elements. These combina- 
tions are chiefly as oxids, sulphids, carbonates, and silicates, 
and in one or more of these four forms may the great mass 
of metals contained in the earth's crust be found. 

Metallic sulphates are found to a considerable extent. 
Calcium sulphate is of particular interest, occurring as gypsum, 
CaS04.2H20. Upon heating, the two molecules of water of 
crystallization may be driven off, leaving the anhydrous CaS04, 
or plaster of Paris, so largely used in dental laboratories. When 
water is added to the anhydrous powder it reunites in the pro- 
portions of the original crystallized salt and thereby occasions 
i\\e '' setting " of the plaster. Essig states that if in the prep- 
aration of plaster the heat is allowed to exceed 127° C, its 
affinity for water is impaired or destroyed and this effect ^^ill 
not be produced.* 

As plaster sets, more or less expansion will take place, and 
if spread upon glass, the mass usually rises slightly in the cen- 
ter, producing a plate which is somew^hat concave on the under 

* American Text-book of Prosthetic Dentistry. 

59 



60 



DENTAL METALLURGY. 



surface. This tendency to expansion varies with different 
grades of plaster, as may easily be shown by a method sug- 
gested by Dr. George H. Wilson in the Dental Cosmos for 
August, 1905, page 940, which consists simply of fiUing small 
glass beakers with mixtures similarly prepared. Some samples 
were found to expand so sHghtly as not to injure the glass, 
others cracked, and some broke the beaker into fragments. 

The method of mixing also affects the amount of expan- 
sion. In a valuable article on ^^ Experiments in Plaster of 
Paris to Test Expansions," by Dr. Stewart J. Spence, in Items 
of Interest, 1902, page 721, it is shown that ^' not only do 
different plasters expand in differing degrees, but the same 
plaster expands very differently according to the stirring given 
it before pouring," and that long stirring increases the heat 
developed, the rapidity of setting, and the amount of expan- 
sion, but decreases the strength. 




An apparatus which may be used for testing the expan- 
sion of plaster is represented by Fig. 4. The plug H is screwed 
into the cylinder K, which is then filled with the fresh mixture 
of plaster and water. The piston P is inserted and the whole 
placed in the trough C. A pin above the post B passes through 
the hole H, holding it perfectly firm at this end. At the other 
end the sliding section D is brought up firmly against the 
end of P and the needle set at 0. Any expansion of the plaster 



THE METALS. 61 

must manifest itself in the only direction possible by pushing 
out the piston P and indicating on the dial the degree of expan- 
sion. The needle is turned by a rack and pinion connected 
with E. The action is very easy, and the mechanism so arranged 
that the slightest expansion is readily indicated by the needle. 
By placing this apparatus on the second base M this same 
apparatus may be used to test the strength or contraction 
of dental floss, ligatures, etc. The silk is fastened firmly at A, 
then passed through the hollow glass tube T, which is of the 
proper length to allow the silk to be again fastened at D. It is 
then passed back of the dial and over F, and if desired a weight 
attached. The tube T is then filled with water, which by 
capillary attraction retains sufficient moisture to keep the 
thread wet. As the thread thickens it contracts longitudinally, 
pulling the needle to the left, and comparative tests may be 
made and continued for as long a time as necessary. 

Various methods have been prepared to overcome the diffi- 
culties in manipulation of plaster, such as mixing the plaster 
with alum, marble-dust, or potassium sulphate. A com- 
pound on the market consists of a mixture of plaster and 
Portland cement. A mixture which has been very strongly 
recommended as an investment preparation consists of two- 
thirds plaster and one- third powdered pumice-stone. 

Other natural sources of the metals are phosphates and 
chlorids, also smaller amounts of nitrates and comparatively 
slight amounts of bromids, iodids, and fluorids. The metals 
are extracted from their ores chiefly by reduction with some 
form of carbon. In case of the oxids this reduction takes place 
directly, according to this reaction: 2CuO + C = 2Cu + C02. 

In case the metallic combination is a sulphid, the ore is 
first '^ roasted " in the air, whereby the sulphur is burned off 
and an oxid is formed, which may then be reduced as above: 
2CuS + 302 = ^C^^O + 2S02. 

The native carbonates are reduced to oxids by calcination, 
as CaCOa + heat = CaO + CO2. 



62 DENTAL METALLURGY. 

The silicates must first be changed to carbonates by fusion 
with alkali carbonates, then the reduction may be carried on 
as before: 

MgSiOs + NasCOs = MgCOs + NasSiOs ; 
then MgCOs + heat = MgO + CO2. 

Properties of the Metals. 

Metals are malleable in order as follows from gold, the 
most malleable, to nickel, the least: Au, Ag, Al, Sn, Cu, Pt, 
Pb, Cd, Zn, Fe, Ni. 

Metals are ductile from most to least as follows: Au, Ag, 
Pt, Fe, Ni, Cu, Cd, Al, Zn, Sn, Pb. 

Metals conduct heat and electricity in the same order until 
Sn is reached. From Sn the order given is correct for heat 
but not for electricity: Ag, Cu, Au, Al, Zn, Cd, Sn, Fe, Pb, 
Pt, Bi. 

The melting-point of the various metals is of considerable 
importance in the preparation of alloys. The following table 
has been compiled from the latest available results. The 
degrees given are according to the centigrade scale: 

Pt 2000° Cu 1054° Zn 420° (burns) 

Ni 1450° Ag 954° Pb 326° 

Cast steel 1375° Al 700° Cd 320° 

Cast iron 1275° Mg 500° (burns) Bi 268° 

Au 1075° Sb 432° Sn 238° 

The expansion of the various metals under the influence 
of heat is fairly constant and there have been determined 
coefficients of expansion. These represent the amount of 
linear expansion of the metals due to a rise in temperature 
of 1° C, usually from 0° to 1°. The coeflacients are not abso- 
lutely constant, and the amount of expansion observed between 
0° and 1° may differ somewhat from that between 50° and 
51°. The coefficients vary widely for the different metals; 
for instance, in passing from 0° to 100° mercury expands 1/16 
of its finear measure, copper 1/598, and platinum 1/1123. 



THE METALS. 



63 



Hall's Dental Chemistry gives the following table of expan- 
sion from cadmium to platinum: 



C(l., 

Ph. 

Zn. 
Al.. 
Sn . 



l/32() 


Ag 


1/342 


Cu 


1/343 


Ki 


1/432 


Au 


1/448 





1/518 
1/598 
1/017 
1/689 



Ni 

Fe (cast). 

Sb 

Pt 



1/787 
1/934 
1/952 
1/1123 



The only other general property of the metals directly 
affecting their use in dental practice is the electric or galvanic, 
that is, the electropositive or negative relations they sustain 
to one another. 

The metals are electropositive to each other in the fol- 
lowing order from zinc, the most positive, to platinum, the least : 
Zn, Cd, Sn, Pb, Fe, Ni, Bi, Sb, Cu, Ag, Au, Pt, and C. 

Thus if a battery is constructed with Zn as represented 
in the cut (Fig. 5), and iron in place of the carbon, then the 
iron will be electronegative to the zinc, and 
hydrogen will be evolved from its surface; if, 
on the other hand, Fe is used in place of the 
zinc, and the carbon remains as in the cut, the 
Fe will be electropositive to the carbon, and 
oxygen will be evolved from its surface. This 
property of metals has a direct bearing upon 
dental science, because human saliva may be 
an exciting fluid for the generation of galvanic 
currents, its activity being increased by an 
abnormal reaction either acid or strongly alkaUne, and it is 
only necessary to place in the mouth properly related metals, 
as amalgam fillings or otherwise, to produce the elements of 
a galvanic battery. 

The currents thus generated are of course infinitesimal, 
but they are constant and may aid in the disintegration of 
fillings and in the solution of the constituent metals. Regard- 
ing the extent to w^hich electric currents may exist in the 
mouth, see Miller's Microorganisms of the Human Mouth. 




Fig. 5. 



64 DENTAL METALLURGY. 

SECTION II.— ALLOYS. 

An intimate union of two or more metals, usually pro* 
duced by fusion, forms an alloy. Such a union of one or more 
metals with mercury is an amalgam. 

An alloy designed to be used in the preparation of dental 
amalgams is known as an amalgam alloy. 

Some metals can be fused together in all proportions, as 
Pb and Ag. Others can be made to unite only in limited pro- 
portions, as Pb and Zn. Lead will carry only 1.6% of zinc^ 
while zinc will unite with only 1.2% of Pb. Excess in either 
case separates out. 

The properties of an alloy are, as a rule, the modified proper- 
ties of its constituent metals. An exception to this rule might 
be made of the sonorous quality of bell-metal and like alloys, 
this being hardly a property of the constituent metals at alL 

Following are some of the more common alloys. The 
proportions given are general formulae and may, as a rule, be 
varied considerably: 

Aluminium bronze, yellow, resembles gold, Cu 92, Al 8. 

Bell-metal, Cu 80, Sn 20. 

Britannia metal, Cu 2, Sn 82, Sb 16. 

Coin silver, Ag 90, Cu 10. 

Dental alloys, see pages 71 and 73. 

Dental gold, Cu 85, Zn 15. 

German silver, Cu 50, Ni 30, Zn 20. 

Composition of different samples of German silver may 
differ widely; some contain about 2.5% of iron and the amount 
of Cu may vary from 40 to 60%. 

Solder, see page 79. 

Sterling silver, must contain 92.5% Ag. 

Type metal, Pb 78, Sb 15, Bi 7. 

All alloys (excluding amalgams) are solid at ordinary tem- 
peratures with one exception; this one is an alloy of one part 
potassium with three parts sodium. 



ALLOYS. 65 

The melting-point of an alloy is often lower than that 
of the metals entering into its composition and usually 
lower than the mean melting-point of its constituents. 

In making alloys the tendency to separation of the several 
metals is greater if the alloy is allowed to cool slowly; hence 
three essentials in the process are: Complete fusion, which 
makes possible thorough mixing, and after this has been attained 
rapid cooling. As the fused mass is to be cooled as (juickly 
as possible after fusion is complete, it is desirable to use the 
least amount of heat practicable in effecting the desired result. 
To this end fuse first the metal with the lowest melting-point, 
then add other metals in the order of their melting-points. 
The more difficultly fusible metal will in a sense dissolve in 
the more easily fusible metal, an alloy is formed and its tem- 
perature has been kept far below the melting-point of the 
high fusing constituent. This general rule, however, may 
be modified by the proportion of metal used; thus, in making 
a silver-tin amalgam alloy containing 60% of silver it is better 
first to melt the silver under a flux of carbonate of sodium 
or borax to prevent superficial oxidation, then add the tin, 
and lastly any other metal to be used. The mixing is attained 
by stirring with a wooden stick and the cooling by turning 
quickly into a cold clean mold. For class work or in making 
small amounts (20 grams) of alloy, the Fletcher melting arrange- 
ment shown in Fig. 6 is very convenient. The metals are 
melted in the graphite crucible and then by 
tipping up the whole contrivance the melted 
metals flow back into the ingot mold. If the 
alloy is to be used in the preparation of dental 
amalgams it must be reduced to fine turnings or 
filings suitable for ready amalgamation. This is 
best accomplished in the laboratory by means 
of a coarse file, the ingot being held by a vise, 
particles of iron must next be carefully removed with a 
magnet, and then the fiUngs may be annealed if desired. 




66 DENTAL METALLURGY. 

The annealing of the amalgam alloys may be accomplished 
by placing the freshly cut sample in a dry test-tube and 
keeping the test-tube in boiling water for ten or twelve minutes. 
It has been claimed that this process is one of superficial oxi- 
dation and the changes produced seem to be consistent with 
this theory. Again, it is claimed that the change is a molec- 
ular one of some sort due to change of temperature, and 
Prof. G. V. Black has shown that an alloy will anneal as rapidly 
in an atmosphere of nitrogen as of oxygen. The modification 
of properties produced by anneahng varies somewhat with 
the composition of the alloy; for instance, the liability to 
discoloration is less in the annealed than in the unannealed 
sample if the alloy contains Ag and Sn, or Ag, Sn and Zn, 
but if Cu is a constituent the reverse condition has been found 
to exist. 

According to Prof. Hall of Northwestern University '^ an- 
nealed alloys take up less mercury than unannealed and yield 
upon mixing a greater quantity of dirt, which consists of a 
lower oxid of tin." The amalgam made from an annealed 
alloy works more easily than from an unannealed. 

The process of annealing up to a certain point seems to be, 
in general, beneficial; but beyond this point it may be detri- 
mental, the amalgam being less strong and more liable to 
shrink. 

Prof. Black has shown that while it may be possible to stop 
the process of annealing at such a point that a given alloy 
will neither shrink nor expand, it is easy to carry the process 
too far and the farther it has been allowed to go the greater 
the shrinkage. It is probably true that the exact effect of 
anneahng will vary with the composition of the alloy, and 
with different proportions of metals in alloys of the same gen- 
eral composition. 



AMALGAMS. 67 



Annealing of Gold. 



When gold-foil is heated to redness it recovers the cohesive 
property which has been lost largely by hammering. It is 
recommended that the heating be done in an electric furnace 
or on plates of mica or platinum, thus insuring uniformity of 
effect throughout the mass which it is practically impossible 
to obtain by holding the metal in the flame. See Dental 
Cosmos, Vol. XLVII, page 233. 

Non-cohesive gold or gold in which the cohesive property 
cannot be developed by heating may be prepared by alloying 
or treatment with carbon. Corrugated gold is of this variety 
and is prepared, according to Essig, by carbonization of unsized 
paper in intimate contact with the metal. See Essig, Dental 
Metallurgy, page 173. 

In annealing platinum a high degree of heat is required, 
but the heat should be raised gradually, and in this case also 
the electric furnace furnishes an ideal method. 

SECTION III.— AMALGAMS. 

In general, amalgams may be made in three different ways: 
First, by direct union of the constituents as in the manufacture 
of sodium amalgam (page 69); second, by electrolysis of 
strong solutions of metalhc salts in presence of mercury (as 
in copper amalgam, page 70), and third, by double decom- 
position as illustrated in the preparation of ammonium amal- 
gam (page 69). 

Amalgams possess the peculiar property of '' setting " 
or hardening within a short time after mixing. This in some 
cases seems to be a process of crystallization, and in all cases 
is probably due to molecular rearrangement of some sort. 

After an amalgam has '' set " to a sufficient extent to 
make it hard to work it may be softened by application of 
gentle heat. Continued reheating is detrimental to the quality 



68 



DENTAL METALLURGY. 



of the amalgam, and should be avoided; this is particularly 
true of copper amalgam. It is also possible to sometimes 
restore the plastic quality of an amalgam by adding a further 
slight amount of mercury, but the union of the second lot 
of Hg after the first has partly hardened is very unsatisfac- 
tory and results in a weakened product. 

Flow of Amalgams.— This property may be defined as the 
tendency to flatten or change shape under stress or pressure. 
It is common to most amalgams (copper amalgam being an 
exception according to Dr. Black), and is possessed by many 
alloys other than amalgams. 

Tests for " flow " may be made with the '' dynamometer " 
on cubes of alloy or amalgam measuring one tenth of an inch 
each way and the results expressed in percentage of increase 
or decrease of one dimension. The dynamometer used for 
this purpose is pictured in Fig. 7 and is a modification of tha 




Fig. 7. 

apparatus devised by Dr. Black and described on pages 408, 
409 of the Dental Cosmos, Vol. 37, A-A being the molds in 
which the cubes of amalgams are set and B the point in the 
apparatus where the cube after setting is introduced with a 
pair of fine forceps. The dial is supplied with two hands, 
one which flies back the instant the cube breaks, the other 
remaining to indicate the number of pounds applied necessary 



AMALGAMS. 69 

to crush the cube. The cubes of 1/10 inch are best suited 
for students' practice, with a dial constructed to record 250 
pounds pressure. For accurate comparisons of thoroughly 
made amalgams the cubes nmst be made smaller. 

Binary amalgams, as they are sometimes called, are those 
consisting of only one metal besides mercury. These are 
rarely used in dental practice, but from them the properties 
of the amalgamated metal are most easily observed. 

Sodium amalgam may be made by direct union of the 
constituent elements. The mercury should be placed in an 
open dish under a hood, and the sodium added in small well- 
cleaned pieces. 

The union is accompanied by a slight hissing noise, an 
elevation of temperature and evolution of vapor carrying 
more or less mercury, hence dangerous to breathe. An amal- 
gam containing 1% sodium is a viscid liquid; if it contains 5% 
sodium it is a hard solid and intermediate percentages give 
varying degrees of firmness. Sodium amalgam if made with 
arsenic-free Hg is a very convenient reagent to use in making 
Fleitmann's test (page 11). 

Ammonium amalgam has no use in dentistry, but it is of 
interest in that it is the nearest approach to which we may 
attain to the isolation of the purely hypothetical metal ammo- 
nium. It is easily made by adding sodium amalgam to a 
cold saturated solution of ammonium chlorid, thus illustrating 
the third general method of preparation of amalgams. It 
rapidly decomposes at ordinary temperature with the hbera- 
tion of free hydrogen, ammonia-gas, and metallic mercury. 
The H thus hberated exhibits the properties of nascent H, 
indicating that in the amalgam it existed in true chemical 
combination, that is NH4, rather than in any physical solu- 
tion. At ordinary temperature ammonium amalgam is a soft, 
pasty, very porous mass, but at much reduced temperature 
it becomes solid and crystalline, although at -39° (the freezing- 
point of Hg) H and NH3 are still given off. 



/O DENTAL METALLURGY. 

Copper amalgam is by far the most valuable of this class 
of amalgams. It may be made by amalgamating precipitated 
copper after moistening it with nitrate of mercury (Essig). 
The precipitated Cu may be prepared by metalUc Zn in a 
slightly acid copper sulphate solution, but must be thoroughly 
washed with hot water to free it from zinc chlorid. The 
amalgamation may be effected by use of mortar and pestle. 
Rollins' method * by electrolysis of strong copper sulphate 
solution is rather unwieldy, but illustrates very well the second 
general process for the manufacture of amalgams. 

Copper amalgam, according to Black, is absolutely rigid 
after it has once set and does not flow even to a slight extent. 
It is fine-grained and very hard. It is reduced in strength 
by reheating, does not expand or contract. In the mouth 
copper amalgam dissolves with comparative rapidity owing 
to the ready formation first of copper sulphid, then the oxi- 
dation of this compound to the sulphate. It blackens rapidly 
and in consequence of the tendency to dissolve just mentioned^ 
it may penetrate the dentine and thus discolor the tooth itself. 

Gold amalgam is readily made, but does not, by itself, harden 
well. An amalgam containing one part of gold to six of mer- 
cury will crystallize in four-sided prisms (Litch). 

Platinum amalgam is very smooth, is formed with diffi-^ 
culty unless the Pt is very finely divided, and like gold does, 
not harden well. 

Silver amalgam, easily made but tends to expand. 

Tin amalgam, alone shrinks badly. 

Zinc amalgam, readily made, is white, but too brittle to 
be of service. 

Cadmium amalgam may be easily made at ordinary tem- 
perature, '' sets quickly and resists sufficiently, but fillings 
containing it, gradually soften and disintegrate and may 



* Details of this method may be found in the Boston Medical and Surgical 
Journal , February, 1886; also in Mitchell's Dental Chemistry. 



AMALGAMS. 71 

stain the dentine bright yellow by formation of cadmium 
sulphid" (Mitchell). 

Effect of Various Metals in Amalgam Alloys. 

With the properties of these simpler combinations before 
us it becomes easy to understand the effect the addition of 
the various metals will have upon the properties of a silver- 
tin alloy; for practically all amalgam alloys are silver-tin 
alloys, either simple or combined with one or more other metals. 

Silver is the most valuable constituent of amalgam alloys. 
It is essential to the proper setting and hardening of the amal- 
gam. In an amalgam it tends to increase expansion and 
to hasten setting, while tin possesses the opposite character-- 
istics. Combined with tin in the proportion of 65% silver 
to 35% tin, it forms an amalgam alloy perhaps more largely 
used than any other. It was this combination that Dr. Black 
succeeded in " annealing to zero," that is, so that upon test- 
ing, it showed neither expansion nor contraction. 

Pure silver-tin alloys will flow from 2.5 to 10%. 

Authorities seem to agree that if a Ag-Sn alloy contains 
75% or more of silver it will expand only; while an alloy 
containing 50 to 61 or 62% of silver will shrink only; and 
one containing less than 50% of silver will first shrink and 
then expand. 

The larger the proportion of tin the easier will the alloy 
cut, but the coarser will be the filings. 

Zinc added to a silver- tin alloy tends to whiten the amalgam, 
hastens setting, increases the flow, and according to Essig, 
" causes a great but slow expansion." 

Cadmium, see above. 

Antimony gives a fine grain alloy and when the Ag is less 
than 50% is supposed to control shrinkage. 

Bismuth will increase the flow of the amalgam; it is some- 
times used in low-grade Ag-Sn alloys to control shrinkage. 



72 DENTAL METALLURGY. 

Copper tends to diminish flow and gives a strength under 
pressure, sets quickly, gives better margins, and by some 
believed to have preservative influence on the tooth sub- 
stance, but the more copper in an alloy the more rapidly does 
it discolor. 

Gold — Three to seven per cent, of Au in a silver- tin alloy 
diminishes shrinkage^ helps the color, adds to crushing strength. 
The filing from such an alloy will be very fine. 

Dr. Black says 5% of gold gives a softer working property 
but retards setting of the amalgam, and makes it otherwise 
difficult to give a good finish to the filling (Dental Cosmos, 
Vol. 38, page 988). 

Platinum, according to Black, is not a desirable addition 
to a silver- tin alloy. It gives an alloy, furnishing very fine 
filing, which produces a dirty working, slow-setting amalgam. 

Excess o Mercury. — In the preparation of an amalgam 
from a dental alloy it is usual to add more mercury than the 
finished product requires and then squeeze out the excess between 
the fingers or otherwise. In filling a cavity, still more mercury 
is forced out, so that the composition of the deeper portions 
of a filling varies from the outer and probably accounts for 
the inequalities in expansion or contraction. The excess of 
Hg from the surface of a filling may be absorbed by a little 
hot gold or pure tin or by finely divided silver. 

The excess of mercury which has to be squeezed out of 
an amalgam carries with it more or less of the constituent 
metals. Hall found that whatever the amount of mercury 
expressed, it carried just about 1% of tin. In the author's 
experience this amount has reached nearly 1J% of tin. Sil- 
ver is carried out to a much less extent than tin, so it is not 
impossible to carelessly make an amalgam and squeeze out 
enough mercury to change the proportion of Ag and Sn in 
the alloy. This change will, of course, be very shght, but 
we have seen that the contraction and expansion of amal- 
gams may be affected by slight changes in composition. 



AMALGAMS. 



73 



Following is a short list of dental alloys, most of which 
may be easily prepared: 



Arington's (8. 8. W^liite'.s) 

Chase copper-amalgam alloy. . . . 

Chase's incisor 

Flagg's submarine 

Fletcher's gold alloy (old) 

High-grade alloy (7i% gold). . .. 

Harris' amalgam alloy 

King's Occidental 

Standard dental alloy (Eckfeldt). 

60% silver alloy 

Temporary alloy 



8n 


Ag 


Au 


Cu 


Zn 


57.5 


42.5 








50 


50 




10 




40 


50 








35 


00 




5 




56 


40 


4 






41.5 


49 


7.5 




2 


48.1 


40 




4.9 


7 


54.75 


42.75 






2.5 


40.6 


52 


4.4 


3 




40 


60 








88 


10 






2 



8 b 



These formulae have been selected from various sources 
with a view to giving the student opportunity to study effects 
obtained by varying percentages of Sn and Ag, and by intro- 
duction of other metals, Cu, Zn, etc. 

Tests for Amalgams. 

Color Test. — This is made upon a freshly amalgamated 
alloy, rolled into about the shape and size of a small pea, with 
a view to determine the amount of discoloration the amalgam 
is liable to undergo in the mouth. 

A ball of amalgam carefully smoothed on at least one 
side is placed for forty-eight hours in a saturated solution 
of hydrogen sulphid, and after that time its color is com- 
pared with other amalgams similarly treated, or with amal- 
gam of a similar composition which has not been treated at 
all. 

Test for Expansion or Contraction. 

Black has shown that tests of this nature to be of any 
value must be made in such a way that the amount of change 
in the volume can be measured, and that the simple method 
of packing glass tubes and using colored ink is w^holly unreli- 
able. 



74 



DENTAL METALLURGY, 



The author uses for this purpose an apparatus sunilar to 
one described by Prof. Vernon J. Hall. The amalgam is 
packed closely into a '' well " in a steel block, then the block 
is placed in the apparatus so that a counterpoised steel plunger 
rests on the column of amalgam. Tliis plunger is operated 
by a very long needle and attached at a point so near the 
pivotal support of the needle that a rise or fall of the plunger 
of 1/2500 of an inch moves the tip of the needle, at the scale, 
1/16 of an inch, or one degree. If the needle rises half a degree, 
which may easily be read, it would indicate an expansion 
of the amalgam of 1/5000 of an inch. 

There are two wells in each block and both of exactly 
the same depth. The figure given below will make this expla- 
nation easily understood, A being the steel block carrying 
the amalgam. 




Fig. 8. 



Test for Crushing Strength and Flow. — This test is made 
with Dr. Black's dynamometer (page 68) upon cubical blocks 
of amalgam which have been allowed to '' set " for at least 
five days, and which measures 1/10 of an inch each way. 

Specific gravity may be obtained by weighing the sample 
first in water, then in air, and dividing the weight in air by 
the difference between the two weights obtained. 

It is instructive to make these tests on amalgam from 
alloys of varying composition, also on annealed and unannealed 
alloys of the same composition. 



DENTAL CEMENTS. 75 



SECTION IV.— DENTAL CEMENTS. 

Dental cements, largely used as temporary fillings and 
linings of cavities, contain oxid of zinc, oxid of copper (rarely 
sulphate of zinc) combined (at the tune the cement is used) 
with phosphoric acid or with a solution of zinc chlorid. 

There are six forms of dental cements which might be 
mentioned: the oxyphosphate of zinc, oxyphosphate of cop- 
per, artificial enamel, oxychlorid of zinc, oxysulphate of zinc, 
and tin cement. Of these, the last three are but little used. 

Oxyphosphate of Zinc. — This is the most serviceable of 
the preparations of this class unless exception is made of the 
new artificial enamels, which have not been in use long enough 
to warrant positive assertions as to their comparative value. 

The oxyphosphate cement is usually made by adding a 
powder, consisting of pure oxid of zinc, colored by a slight 
amount of other metalUc oxids, to a hquid consisting of 
deliquesced phosphoric acid (or a solution of phosphoric acid 
in which zinc phosphate, and possibly slight amounts of other 
phosphates, have been dissolved), till a putty-like mass results, 
which rapidly hardens and becomes capable of receiving a 
considerable polish. When the phosphoric acid used is the 
glacial acid, the cement may be spoken of as a metaphosphate, 
as the glacial acid, before the addition of water, and to a cer- 
tain extent afterwards, is actually metaphosphoric acid, HPO3. 
The metaphosphoric acid by boiling in water or gradually 
without boiUng becomes the orthophosphoric acid (H3PO4). 

Arsenic is a frequent impurity in both zinc oxid and phos- 
phoric acid, and if present is very liable to produce an irri- 
tating cement, sometimes causing considerable trouble, hence 
the material entering into the composition of any dental 
cement should be free from arsenic (see pages 10 to 13 for 
arsenic tests). 

The purer the zinc oxid and the phosphoric acid, from 



76 DENTAL METALLURGY. 

which the cement is made, the more durable it is found to 
be; so aside from any question of irritation, it is quite necessary 
for the sake of the cement itself that the ingredients be pure. 

A pure ZnO may be made by calcining the precipitated 
carbonate of zinc, Zn5(OH)6(C03)2 + heat = 5ZnO f 2CO2 + SHsO. 
The heat should be below 500° F., because if two strongly heated, 
the color suffers, becoming yellowish. 

Another method of making pure oxid of zinc is given as 
follows: Dissolve pure zinc in nitric acid, evaporate to dry- 
ness, and heat till fumes cease to be given off. The mechanical 
effect of the escaping oxids of nitrogen is said to leave the 
ZnO in the form of a very fine powder. 

A pure phosphoric acid can be made from the ortho-acid 
by heating till the white fumes begin to come off, then heat 
to redness, cool, and dissolve in H4O to a thick syrup. In 
mixing cements the powder should be worked into the liquid 
till the desired consistency is obtained. 

Oxyphosphate cement and all cements having zinc oxid 
for a base tend to dissolve in the fluids of the mouth, lactic 
acid and ammonium salts being particularly good solvents for 
this class of compounds. The addition of ferric oxid to oxy- 
phosphate cement increases resistance to disintegration. One 
part of ferric oxid to 6 to 10 of zinc oxid is recommended by 
Rollins in the International Dental Journal. 

Oxychlorid of zinc is more easily soluble than oxyphos- 
phate. It shrinks more, but is credited with a preservative 
action on dentine and hence used to some extent as a lining. 

The powder of the oxychlorid cement is ZnO with some- 
times a little borax, or silica, or both, added. A good oxy- 
chlorid cement will set in fifteen or twenty minutes, but keeps 
on growing harder for several hours. The following formula 
is recommended. 



DENTAL CEMENTS, 77 



OxYCHLORiD Cement. 



Oxid of zinc 10 grams, borax 0.1 gram, and powdered 
silica 0.2 gram. 

Transfer to clay crucible and calcine for one half hour 
in furnace at bright-red heat. Pulverize, sift, and bottle. 
The liquid to be used with this powder consists of 10 c.c. of 
pure liCl saturated with pure zinc and filtered through glass 
wool. 

Oxysulphate of Zinc. — This is used still less than the oxy- 
chlorid. It is non-irritating, dissolves easily, and is com- 
paratively soft. The following formula is from Hall's Dental 
Chemistry. 

Oxysulphate Cement. 

Ten grams oxid of zinc, 4 grams sulphate of zinc. Dry, mix, 
calcine for one half hour and sift. 

Liquid to be used with the powder may be made by dis- 
solving 2 grams of zinc chlorid in 10 c.c. of water. This gives 
a turbid solution and should be shaken when used. 

Oxyphosphate of Copper. — A preparation by this name 
which has been used to a considerable extent in the vicinity 
of Boston has been examined by the author and found to 
consist of the usual powder and liquid. The powder (coal- 
black) was composed of a mixture of the oxids of copper, 
iron, cobalt, and zinc, the liquid being phosphoric acid 
containing zinc phosphate in solution. 

The cement resulting from this combination was found 
to be hard, showing practically no change of volume and 
resisting the solvent action of the saliva. 

Tin Cement. 

Dr. Arthur Scheuer, of Tephtz, Bohemia, recommends a 
preparation composed of a finel}^ pulverized tin sponge and 
zinc oxid mixed with glacial phosphoric acid. '^ The powder 



78 DENTAL METALLURGY. 

is of a light-gray color, becoming slighth^ darker when mixed 
with the acid, but regains its original color after setting. A 
tin-cement filUng can be easily inserted and when polished 
it has a metalHc appearance." (Dental Cosmos, May, 1904.) 

Artificial Enamel. — Several preparations have recently 
been put on the market under this name with the claim that 
it makes a much harder cement and one which resists disin- 
tegration to a much greater extent than the ordinary zinc 
preparations. 

The specifications of a German patent, under which one 
of these preparations is manufactured, claims that the powder 
consists of a mixture of the oxids of beryllium and sihcon, 
together mth alumina and lime. The liquid consists of a 50% 
solution of orthophosphoric acid in which aluminium phos- 
phate and zinc phosphate have been dissolved. 

When mixed in the usual manner these produce a cement 
which is much harder and less soluble than any of the prepa- 
rations pre\dously considered. 

An advertisement of one of these preparations claims that 
its success is due to the use of a very valuable compound, 
without which it would be worthless, and so far as the author 
has had opportunity to investigate this subject, this state- 
ment seems to be true. A qualitative analysis confirms the 
claim of the patent specifications both in regard to the com- 
position of the liquid and the presence of oxid of beryllium 
in the powder, and it is probable that the value of these prep- 
arations depends largely upon the proportion of beryllium 
entering into their composition. 

BerylHum is one of the rare metals which occurs naturally 
with aluminium as a silicate. It forms basic compounds of 
such character as makes it suitable for use in dental cement. 

The cement powders may be tested for beryllium as fol- 
lows: Fuse a little of the powder with sodium carbonate (or 
the double sodium potassium carbonate); dissolve the fused 
mass in dilute hydrochloric acid; evaporate to dryness and 



SOLDERS. 79 

heat to 120° C. to dehydrate the sUica; take up in water with a 
little HCl and filter; to the filtrate (probably containing Al, 
Be, Zn, and Ca) add a little ammonium chlorid, and an excess 
of ammonium carbonate, A1(0H)3, Be(0H)2, and CaCOa, will 
be precipitated. The beryllium, however, is easily soluble in 
the excess of (NH4)2C03. AVarm (not boil) and allow to stand 
for some time to insure complete separation of Al. (Xotc. — 
A1(0H)3 is much less soluble in solution of (NH4)2C03 than 
in either NH4OH or even NH4OH and NH4CI.) Filter. Boil 
the filtrate for a long time, when the beryllium and some zinc 
will be precipitated. Filter and dissolve precipitate off paper 
in dilute HCl. To the filtrate containing BeCl2 and ZnCl2 add 
NH4CI in excess and NH4OH, which will give a precipitate of 
Be (OH) 2'. If Be and Zn only are present, the separation by 
boiling may be unnecessary. 

The liquid may be tested for dissolved phosphates by 
diluting with water and adding ammonia till alkaline; if the 
mixture remains clear, phosphates of alumina, calcium, or 
zinc are absent. Care should be used, however, in the addi- 
tion of the ammonia, as an excess of this reagent will redis- 
solve phosphate of zinc. 

If the ammonia is too strong, a precipitate of ammonium 
phosphate may be obtained, but this may be easily redis- 
solved by the simple addition of water. 



SECTION v.— SOLDERS. 

Solders are alloys used in joining pieces of metal of the 
same or of different kinds. One of the constituent metals 
of the alloy forming the solder is usually the same as the sur- 
face upon which it is to be used, hence the various metals 
require solders of special composition; for instance, common 
solder is entirely unsuited for soldering aluminium or gold. 

Common Solder is composed of tin and lead in different 



80 DENTAL METALLURGY. 

proportions. The larger the proportion of tin the finer is 
the solder, and the following three grades may usually be 
obtained: " Fine " (tin two parts and lead one), '' Common " 
(tin and lead equal parts), '' Coarse " (tin one part and lead 
two parts). 

In soldering metals it is absolutely essential that the sur- 
faces are kept clean and free from superficial coating of oxids 
which may form easily with the elevated temperature employed 
in the process. Soldering acid and the various fluxes serve this. 
purpose. Soldering acid is an acid solution of zinc chlorid 
usually made by taking a few ounces of strong hydrochloric 
acid and adding zinc as long as the metal dissolves. Among 
the substances w^hich may be used as a flux to prevent oxi- 
dation, rosin and borax are the most common. 

Soft Solders are those fusing below a red heat and include 
the common solders above mentioned, also the most fusible 
solders containing bismuth. These last are more properly 
fusible metals and will be discussed under that head. 

Solders for Aluminium. — Aluminium solders with consider- 
able difficulty owing in part to the low melting-point of the 
metal, also to the fact that aluminium is attacked by alkali, 
including borax, which makes it necessary to find some sub- 
stitute for this convenient flux. Essig recommends a flux 
consisting of three parts of copaiba balsam, one part of Vene- 
tian turpentine, and a few drops of lemon-juice. The mix- 
ture is to be used in the same manner as soldering acid with 
a solder consisting of zinc 80 to 92 parts, aluminium 8 to 20 
parts. Fused and finely powdered silver chlorid may also 
be used as a flux, the salt being reduced and the silver form- 
ing a superficial alloy. Richards recommends a solder for 
aluminium consisting of tin 29 parts, zinc 11 parts, aluminium 
1 part, phosphor-tin 1 part. 

Hall says that a solder which he has found very satisfactory 
may be prepared from aluminium 45 parts, tin 45, mercury 10; 
further, that the following formul2e suggested by Schlosser 



SOLDERS. 81 

are particularly adapted to soldering dental work since they 
resist the reaction of corrosive substances. 

Plat in urn- Aluminium Gold- Aluminium 

S(jider. Solder. 

Gold 3 parts Gold 5 parts 

Platinum 0.1 part Copper 1 part 

Silver 2 parts Silver 1 " 

Aluininium 10 " Aluminium 2 part.s 

For soldering articles of aluminium the following solder 
is given in the Pharmaceutical Era, January 10, 1895: Sil- 
ver 2, nickel 5, aluminium 9, tin 34, and zinc 50 parts, to be 
used without flux. 

Solder for brass requires a high heat for fusion and on 
this account is known as hard solder. 

Edwinson gives the following formulae: (1) copper 13 
parts, silver 11; (2) copper 1 part, brass 1, silver 19; (3) brass 
5 parts, zinc 5, silver 5. The flux for brass soldering is powdered 
borax, which may be mixed with water to a paste and applied 
with a feather or a small brush. 

Solder for Gold.— Gold soldering is the most particular 
work of this class which the dentist has to do. There are a 
few requirements for a good gold solder which might be noted 
and which are also applicable to the other solders mentioned: 
(1) The color should be as nearly as possible that of the metals 
upon which it is to be used. (2) The solder should have a 
fusing-point but very slightly below that of the metal to be 
soldered. (3) The solder should flow freely. 

Litch gives the following instruction for making a zinc-gold 
solder which will have the above-mentioned properties: 

" To make the zinc-gold solder take 1 pennyweight of the 
same gold upon which it is to be used and add IJ grains of 
zinc. If this is done in a crucible in the furnace, first fuse 
the gold (which should either be clean scraps or be cut from 
the plate; never use filings for this purpose), using but little 
borax; when thoroughly fused take the crucible in the tongs, 
drop the zijic into it, give the crucible a rather vigorous yet 



82 



DENTAL METALLURGY, 



skilful shake to assist in mixing its contents, but without 
causing any to be thrown out, and immediately pour into 
the previously prepared ingot mold. This must be done 
very quickly or the solder will require too high a heat for the 
fusion on account of a large proportion of the zinc being vola- 
tilized or oxidized and thus be lost as alloy." 

Essig gives the following formulae for alloys of gold employed 
in dentistry as solders: 



No. 1. 14 Carats Fine, 

American gold coin $10.00 

Pure silver 4 dwts. 

Pure copper 2 " 

No. 3. 14 Carats Fine. 

Pure silver 2^ dwts. 

Pure copper 20 grs. 

Pure zinc 35 

18-carat gold plate (formula 

No. 11) 20 dwts. 

No. 5. 16 Carats Fine. 

Pure gold 11 dwts. 

Pure silver 3 " 6 grs. 

Pure copper 2 " 6 " 



No. 2. 14 Carats Fine. 

American gold coin . 16 dwts. 

Pure copper 3 "18 grs. 

Pure silver 5 " 

No. 4. 15 Carats Fine. 

Gold coin 6 dwts. 

Pure silver 30 grs. 

Pure copper. . 20 " 

10 " 



No. 6. 16 Carats Fine. 

Pure gold 11 dwts. 12 grs. 

Pure copper 1 dwt. 12 ' ' 

Pure silver 3 dwts. 

Pure zinc 12 grs. 



No. 7. 18 Carats Fine. 

Gold coin 30 parts 

Pure silver. . . . '. 4 " 

Pure copper 1 part 

Brass 1 " 

No. 8. 20 Carats Fine, for Crown and Bridge Work. 
American gold coin (21.6 carats fine) $10 

piece 258 grs. 

Spelter solder 20. 64 " 

No. 9. 20 Carats Fine, Same Use as No. 8. 

Pure gold 5 dwts. 

Pure copper 6 grs. 

Pure silver 12 

Spelter solder 6 



SOLDERS. 83 

No. 10. 20 Carats Fine, for Crown and Bridge Work. 

Zinc 1^ grs. 

Pure gold 20 " 

Silver solder 3 

No. 11. Dr. C. M. Richmond's Solder for Bridge Work. 

Gold coin 5 dvvta. 

Fine brass wire 1 dwt. 

No. 12. Dr. Low's Formula for Solder for Crown and Bridge Work, 
19 Carats Fine. 

Coin gold 1 dwt. 

Copper 2 grs. 

Silver 4 " 

Solder for Platinum. — Platinum utensils may be soldered 
with any good gold solder, and a flux may be used if desired. 
When, however, the solder, is used in connection with por- 
celain work, it must be pure gold or a gold and platinum alloy. 
A 25% platinum alloy has been found to give excellent results. 
The following in regard to gold and platinum alloy is from 
the Dental Review, August 1905: 

" The colleges and text-books tell us the proper proportions 
of gold and platinum alloys, but they usually fail to tell us 
how to do it. In most cases the platinum appears in white 
spots on the plate without producing a proper alloy. Take 
a small piece of 22-carat gold and fuse it under the blowpipe. 
Then work in all the platinum you can in small pieces until 
it has taken up all that is required. It will produce a small 
button of a white alloy which is very brittle. Add this alloy 
in required proportions to the gold in the crucible and it will 
produce a real platinum alloy. By this method you can make 
clasp gold that is pretty nearly as stiff as a steel spring and 
yet will roll and work without fracture. (Mark G. McElhinney, 
Ottawa, Canada.)" 

The gold " carat " signifies 1/24 part and is used as a meas- 
ure of purity of an alloy, 22 carat gold being 22 24 pure gold. 
20-carat gold is 20/24 pure, etc., etc. The amount of gold in 



84 



DENTAL METALLURGY. 



a given alloy may be determined with considerable accuracy 
by use of a device shown in Fig. 9 much used by jewelers, 
consisting of a series of standard alloys and a piece of stone 
upon which the test is made. The tips are standard alloys. 
Parallel markings are made on the stone with the alloy in 
question and with the tip supposed to correspond to it; then 
the addition of a drop of strong nitric 
acid to the marks and a careful com- 
parison of their appearance will show 
if the two are of the same composition » 
If the composition of an alloy is 
known the value in carats may be de- 
termined by the following 

Rule to determine the carat of a given 
alloy: Multiply 24 by the weight of 
gold used and divide result by total 
weight of alloy. For instance, if an 
alloy is made containing 9 parts of 
gold and 3 of another metal, the 
total weight will be 12 and the cal- 
culations 24x9-^12 = 18. The alloy is an 18-carat gold. 

Gold may be raised to a higher carat by the following rule: 
Multiply weight of alloy used by difference between its carat 
and that of the metal to be added. Then divide product 
by the difference between the carat of the metal added and 
that of required alloy. The figure thus obtained represents 
the total weight of required alloy. Subtract from this weight 
of material taken and difference in weight of pure or alloyed 
gold to be added. (From Hall's Dental Chemistry.) 

To reduce gold to a required carat Essig takes the follow- 
ing rule from Richardson's Mechanical Dentistry: ''Multiply 
the weight of gold used by 24 and divide the product by the 
required carat. The quotient is the weight of the mass when 
reduced, from which subtract the weight of the gold used, 
and the remainder is the weight of the alloy to be added." 




Fig. 9. 



SOLDERS. 83 

Solder for Silver. — Solder for silver usually consists of 
alloys of silver and copper with sometimes zinc and some- 
times tin. Litch recommends a silver solder made by alloy- 
ing pure silver with one-third its weight of brass. '' Brannt's 
Metallic Alloys " give alloys of silver and copper simply. Hall 
recommends silver 8 parts, copper 1, and zinc 2. In the prepa- 
ration of solder containing copper, zinc, or tin, the use of a 
flux is necessary to prevent the formation of metalUc oxid. 
For this purpose borax is usually employed. The silver con- 
stituting, as it does, the greater proportion of the alloy, should 
be melted first and be covered with considerable borax. When 
this has been thoroughly fused, the other metals may be added 
and mixed by agitation or by stirring with wood. Finally, 
the solder may be cast in the usual ingot mold. 

Fusible Metals. 

Under the head of fusible alloys properly come many of 
the alloys previously considered as solders. The fusible alloy 
usually contains lead or bismuth together with tin and occa- 
sionally cadmium. This may be mixed in proportions such 
that the melting-point may be anything desired down to 63° C. 
These alloys are largely used in the dental laboratory. Per- 
haps the most serviceable is known as Mellot's metal, which 
is composed, according to Essig, of bismuth 8 parts, tin 5, lead 3. 
This melts at about the temperature of boiling water. Wood's 
metal, melting at about 65° C, is composed of bismuth 4 parts, 
tin 1, lead 2, and cadmium 1. Rose's metal is bismuth 2 parts^ 
tin 1, and lead 1. This melts at about 95° C. 

Babbitt Metal, much used in the manufacture of dies, is 
composed of copper 1 part, antimony 2, and tin 8. The for- 
mula of common Babbitt metal on the market will be found 
to differ somewhat from the above and is not so well suited 
for dental purposes. 

According to Essig's Dental Metallurgy, '' Dr. C. M. Rich- 



86 DENTAL METALLURGY, 

mond used a fusible alloy in crown and bridge work which 
he states is as hard as zinc and can be melted at 150° F. and 
poured into a plaster impression without generating steam. 
The formula of this alloy is as follows: Tin 20 parts, lead 19, 
cadmium 13, and bismuth 48. The following fusible-metal 
alloys are also suitable for the purpose." 



Tin. 
1 


Lead. 
2 


Bismuth. 
2 


Melting-point of Alloy. 
236° F. or 113° C. 


5 


3 


3 


202° F. or 94° C. 


3 


5 


8 


197° F. or 92° C. 



The fusing-point of an alloy may be determined by melt- 
ing under a liquid of sufficiently high boihng-point and then 
carefully noting the temperature at which the melted alloy 
sohdifies. Care must be taken that the temperature of the 
alloy is exactly the same as recorded by the thermometer. 
To insure this, in the case of an alloy with low melting-point, 
it is usually sufficient to place the alloy in water or brine in 
a test-tube which is immersed in a beaker of similar fluid, then 
by raising the heat gradually with constant stirring and by 
taking the mean of two or three determinations, fairly accu- 
rate results are obtained. 



SECTION VI. -RECOVERY OF RESIDUE. 

Gold. — The gold scrap may be recovered in two ways: 
first, by fusion with suitable flux; second, by dissolving in aqua 
regia and precipitation of the metal. In the first method it 
is necessary to remove mechanically the impurities as far as 
possible, then mix the fairly clean gold waste with potassium 
nitrate and a little borax and fuse in a clay crucible. The gold 
will separate as a button at the bottom of the thoroughly 
fused slag. 

In the second method the scrap gold is dissolved in aqua 
regia and the resulting solution of AuCls is precipitated with 
ferrous sulphate or oxalic acid. The later precipitant, although 



RECOVERY OF RESIDUE. 87 

working more slowly than the iron, does not precipitate plati- 
num, hence in case platinum is present it is the better reagent 
to use. The precipitated gold is next filtered, thoroughly 
washed, and fused in clay crucible under borax and potassium 
nitrate. 

Silver. — The recovery of silver is best accomplished by 
dissolving the scrap or waste in nitric acid and precipitating 
as chlorid, then reducing the chlorid to metallic silver either 
by treatment with pure zinc or by fusion with sodium car- 
bonate. If tin is present in the scrap the nitric acid will form 
metastannic acid, a white insoluble powder rather difficult 
to filter. Hence it is better to wash this by decantation 
several times with distilled water, which will remove prac- 
tically all the silver. From the nitric acid solution the Ag 
may be precipitated by salt or hydrochloric acid. This pre- 
cipitate must be washed till the wash-water is practically 
free from chlorin, then dried and fused with sodium carbonate, 
when a button of pure silver will be obtained. 

If preferred, the precipitated chlorid of silver may be washed 
once by decantation, then agitated with pure zinc, when the 
following reaction takes place: 

2AgCl-^Zn-ZnCl2^2Ag. 

The finely cfi\'ided Ag (in the form of nearly black powder) 
must be washed free from chlorin, carefully dried and fused 
under carbonate of sodimn, or, after drying, it may be weighed 
and fused at once. If the silver residue contains mercury 
this may be driven off by heat before solution is attempted. 

Mercury. — Mercury which has been used in making amal- 
gams is best purified by distillation. ^lercury which needs 
simply to be freed from dirt, dust, or sUght traces of other 
metals may be piu-ified as follows: If a piece of filter-paper 
is fitted closely in a glass funnel, a pin-hole made in the joint 
and the paper thoroughly wetted with water and the mer- 
cury to be purified placed on the paper, the hea\y metal will 



■■■■■ 



S8 DENTAL METALLURGY. 

run through the pin-hole, leaving practically all the dirt cling- 
ing to the wet filter-paper. Such mercury may also be cleansed 
by filtering through chamois-skin. 

In case the mercury contains slight amounts of other metals, 
if it is digested with a very dilute nitric acid, the acid will 
generally first dissolve the impurities and afterwards a little 
of the mercury itself. Then thorough washing of water will 
remove all excess of acid and all soluble salts which may have 
been formed. Pure mercury should have no coating of any 
sort on its surface, and if a few globules are allowed to run 
down a smooth inclined plane, they should leave no ^' tail " 
behind. 



PAKT III. 

VOLUMETRIC ANALYSIS, 



Volumetric analysis is the determination of the quantity 
of a particular substance contained in a given sample by means 
of volumetric or standard solutions. By means of standard 
solutions it is possible to determine easily and quickly the 
strength of a peroxid of hydrogen solution, the percentage 
of silver in an amalgam alloy, or the amount of gold in a plate 
or solder, and it is volumetric analysis thus speciaUzed and 
adapted to dental purposes that we shall consider. 

The standard solution may be so prepared that it has an 
arbitrary or special value, such, for instance, as the silver 
nitrate solution usually used in determining the amount of 
chlorin in urine, 1 c.c. of this solution being equal to 10 milli- 
grams of salt (NaCl); or its standardization may be made 
with reference to the molecular weights of the reagents employed, 
so that solutions of a similar nature will be of equivalent values. 
That is, a solution containing the hydrogen equivalent of the 
reagent, weighed in grams, per liter, is known as a normal 
solution and 10 c.c. of any normal acid will be of the same 
value in neutralizing an alkaU as 10 c.c. of any other normal 
acid. On the other hand, 10 c.c. of a normal acid is equal 
to 10 c.c. of any normal alkali solution whatever the alkali 
may be. 

The normal factor is the weight of reagent contained in 
one cubic centimeter of the normal solution. 

89 



90 VOLUMETRIC ANALYSIS. 

The volumetric process and the use of the normal factor 
will be most clearly understood by the explanation of a specific 
example. 

We will suppose that we have prepared a normal solution 
of NaOH and wish to ascertain the strength of a sample of 
dilute HCl. The normal solution will contain the molecular 
weight in grams of NaOH per liter or 40 grams absolute NaOH. 

The molecular weight of HCl being 36.4 (36.37), a normal 
solution of HCl will contain 36.4 grams absolute HCl, and if 
a liter of normal NaOH were added to a liter of normal HCl 
exact neutralization would result. 

NaOH + HCl = NaCl + H20. 
40 36.4 58.4 18 

The 1 liter of normal alkali (containing 40 grams NaOH) 
is exactly neutralized by 36.4 grams of HCl, or 1 c.c. of nor- 
mal alkali by 0.0364 gram of HCl. 0.0364 is normal factor 
of HCl. 

Now if by our process of analysis we find that it takes 
just 21 c.c. of the NaOH solution to exactly neutralize 10 c.c. 
of HCl solution, 1 c.c. of NaOH being equal to 0.0364 gram 
HCl, 21 c.c. of NaOH will be equal to 0.0364x21, or 0.7644 
gram HCl, or 10 c.c. of the HCl solution contains 0.7644 gram 
of absolute HCl, equivalent, approximately, to 7.64%. 

It has become apparent that in carrying out this process 
three things are absolutely necessary: 

1. Methods for the preparation of standard solutions. 

2. Apparatus for accurate measurements of both the standard 
solution and the unknown. 

3. Means for determining just when the point of exact 
neutraUzation is reached. This point is known as the " end 
point " and is shown by " indicators " of various kinds. 

Preparation of Standard Solutions. — Experience has shown 
that normal solutions are in many cases less convenient to 
work with than those much more dilute, both on account 



VOLUMETRIC ANALYSIS. 91 

of the keeping qualities of the standard solution and the accu- 
racy of manipulation, and for the purposes of dental chemistry 
a decinormal or one-tenth normal solution represented by 
N/10 will generally be used. 

In working with an N/10 solution the factor used in cal- 
culation of results will be one-tenth of the normal factor and 
is termed an N /lO factor. Other fractional proportions of the 
normal solution may be used as the centinormal, N/100, or 
seminormal, N/2. Wiile the decinormal solution contains 
one-tenth of the hydrogen equivalent of reagent in grams 
per liter, and this amount is very easy to calculate, it is often 
very difficult to weigh out the exact amount required. For 
instance, we want an N/10 solution of HCl. HCl is a gas 
soluble in water and the strength of the solutions vary greatly^ 
so we cannot weigh out 3.637 grams of absolute PICl to put 
in 1000 c.c. of water though we know this is just the amount 
necessary to produce our N/10 solution. Thus one of the 
first practical difficulties in making up standard solutions is 
to find some substance which can be weighed accurately and 
whose exact chemical composition may be relied upon. 

Crystallized oxalic acid is such a compound, although with 
this care must be taken that the crystals are dry and yet 
contain all their water of crystallization; in other words, are 
actually represented by the fornmla H2C204,2H20. Fused 
carbonate of sodium is another such compound. If the purest 
obtainable bicarbonate of soda is fused till no further change 
takes place, cooled, and powdered, the product is pure enough 
for the preparation of a standard solution for ordinary use. 

For the preparation of volumetric solutions it is necessary 
to have first a balance which will weigh accurately to at least 
two decimal points; in other words, it must be sensitive to 
1 centigram. Such a balance with silk bearings and which 
the author has found to answer the purpose very well was 
obtained of the L. E. Knott Apparatus Co., Boston (Fig. 10), 
at $12.00 list. 



92 



VOLUMETRIC ANALYSIS. 



Secondly, a flask capable of holding 500 or 1000 c.c. care- 
fully graduated on the neck; also one of 100 c.c. capacity. 




Fig. 10. 



Graduated cylinders (Fig. 11) are not so well suited for the 
preparation of standard solutions, as the greater breadth of 




i 



I 




Fig. 11. 



Fig. 12. 



Fig. 13. 



the column of liquid makes accurate reading much more diffi- 
cult. 

Small cylinders of 100 c.c. are useful in making up odd 



INDICATORS. 93 

amounts of solution, also 50 c.c, 100 c.c, and 250 c.c. gradu- 
ated flasks are very convenient, although not absolutely neces- 
sary. 

In the process of analysis it will be necessary to have 
pipettes (Fig. 12) measuring 5 and 10 c.c, also a burette 
(Fig. 13), from which the standard solution may be used. The 
burettes may be had in a variety of styles and sizes, a very 
serviceable one being of 25 c.c. capacity and graduated in 
tenths of c.c. It may have a glass stop-cock or it may be fur- 
nished with a glass tip with rubber connector and pinch-cock. 

A set of measuring-instruments should be kept which have 
been carefully compared with one another; that is, the 1000-c.c. 
flask should be exactly filled by taking the 100-c.c. flask full 
10 the mark just ten times, thus enabling one to acciurately 
take aliquot parts of any given solution. 

Indicators. 

The third requisite for carrying out a volumetric process 
is a method for determining the end point of the reaction; 
that is, we must know when there has been a sufficient quantity 
of a standard solution added to an unknown solution. Phenol- 
phthalein gives a red color with alkalis, which is discharged 
by the addition of acid till the solution becomes colorless as 
it becomes neutral or acid. Litmus gives a blue color with 
alkalis and a red with acids; Methyl orange can be used with 
carbonates and mineral acids; it does not work as well with 
organic acids. The color is pink in acid and yellow in alka- 
line solution. Lacmoid is useful in cases where the acid proper- 
ties of such salts as alum or zinc chlorid might interfere with 
the use of Htmus or phenolphthalein. The different indicators 
do not all change color at exactly the same point in the process 
of neutralization, and it is possible for a solution to be alka- 
line to litmus and acid to phenolphthalein at the same time. 
Hence uniformity in the use of indicators is desirable. In 



94 VOLUMETRIC ANALYSIS. 

physiological chemistry, Congo red, tropseolin 00, and dimethyl- 
amidoazobenzol are also used. 

The end point may be indicated by excess of a standard 
solution if it happens to be highly colored, as potassium per- 
manganate. Thin starch paste is used as an indicator in 
operations involving the use or liberation of free iodin. Other 
indicators will be considered as we have occasion to use them 
in the various analytical processes. 

The processes of volumetric analysis may be divided into 
three classes: First, acidimetry and alkalimetry. Second, oxi- 
dation and reduction. Third, precipitation. 

Acidimetry and Alkalimetry. 

Acidimetry and alkalimetry includes all standardized solu- 
tions, either acid or alkaline, which may be used in neutralizing 
solutions of unknown strength of an opposite character. For 
instance, the strength of vinegar is determined by neutralizing 
a known volume with standard alkali. 

For present purposes two standard acids and one standard 
alkaline solution will be sufficient. The first of these may be 
decinormal oxalic solution prepared from recently recrystalhzed 
and carefully dried acid. The composition of these crystals 
should be H2C2O42H2O, having molecular weight of 126. This 
being a dibasic acid it will be necessary to divide the molec- 
ular weight by 2 for a decinormal solution and then again 
by 10 to obtain the number of grams, which must be dissolved 
in 1 liter of water. For class use, each student may prepare 
500 c.c. of this solution by dissolving 3.15 grams of pure crys- 
tallized oxaUc acid in water and dilute to a half-liter. The 
graduated flasks are usually constructed to be used at a tem- 
perature of 60° F. or 15° C. and for accurate work solutions 
must be brought to this temperature. After the oxalic acid 
solution has been prepared the decinormal alkali may be 
made as follows: 



ACIDIMETRY AND ALKALIMETRY. 95 

Weigh out carefully 2\ grams of caustic soda or 3 grams of 
caustic potash and dif:solve in something less than 500 c.c. of 
distilled water. After the solution has thoroughly cooled, 
fill a burette with it. Place 10 c.c. of standard acid previously 
prepared in a white porcelain dish of about 250 c.c. capacity, 
add 50 c.c. distilled water and 2 or 3 drops of phenolphthalein 
(2% phenolphthalein in alcohol and water, equal parts), then 
carefully run in fi-om the burette with constant stirring the 
alkali solution until a permanent pink tint is produced. 

The work will be more satisfactory if the titration is made 
for the appearance of color rather than the disappearance of 
color, as would have been the case had the standard acid run 
into the measured alkali solution. This process is known as 
''titration," and will hereafter be so designated. 

The Calculation. — Supposing it has taken 8.2 c.c. of the 
alkali to exactly neutralize the 10 c.c. of N/10 acid, it follows 
that in the 8.2 c.c. is sufficient alkali to equal or to make 10 c.c. 
of an N/10 alkali solution; hence we may add 1.8 c.c. of dis- 
tilled water to every 8.2 c.c. of alkali solution, thereby reducing 
it to decinormal strength. Practically we should take 410 c.c. 
of alkali solution and in a graduated fiask make it up to 500 c.c. 
with distilled water. It will be necessary to make several 
titrations and average the results before making the calculation. 

From the standard alkali N/10 solution of HCl or H2SO4 
may be prepared in a similar manner, it being impossible to 
accurately weigh either of these two acids. In titrating a car- 
bonate, if an indicator, such as phenolphthalein, which is sensi- 
tive to carbonic acid, is used, it is necessary to keep the solution 
at a boiling temperature or at least bring it to a boil after every 
addition from the burette. 



96 VOLUMETRIC ANALYSIS. 



EXAMPLE OF ACIDIMETRY AND ALKALIMETRY. 

Determine the strength of a sample of vinegar as follows: 
Measure accurately into a white porcelain dish of 150-250 
c.c. capacity 1 c.c. of the sample. This may be measured 
either with a carefully graduated 1-c.c. pipette or more accu- 
rately by diluting 10 c.c. of the sample to 100 c.c. in a graduated 
flask, then using 10 c.c. of the dilution for the titration, the 
titration to be performed with N/10 NaOH, using phenol- 
phthalein as an indicator. 

The molecular weight of acetic acid is, in round numbers^ 
60, hence the N/10 factor of acetic acid will be 0.006 (acetic 
acid being monobasic, HC2H3O2), and to ascertain the strength 
of the sample of vinegar it is necessary to multiply the number 
of cubic centimeters used by this factor 0.006, which will give 
the amount of absolute acid calculated as acetic in 1 c.c. (prac- 
tically 1 gram) of the sample. Thus if 8 c.c. of N/10 alkali 
were required to neutrahze 1 c.c. of vinegar, multiplying the 
factor 0.006 by 8 would give 0.048 gram of absolute acetic acid 
in 1 c.c. of vinegar, which is equivalent to 4.8 %. 

Analysis by Oxidation and Reduction. 

If to a hot solution of oxaHc acid containing sulphuric acid, 
permanganate of potash be added, the following reaction takes 
place : 

2KMn04+ 5H2C2O4+ 3H2SO4 = K2SO4 + 2MnS04 + IOCO2 + 8H2O. 

This reaction represents a very valuable method of volu- 
metric analysis, but inasmuch as it is not a process of neu- 
tralization it cannot properly come under the head of acidim- 
etry and alkalinity, but rather under a distinct classification, 
the determination involving oxidation and reduction. 

Standard Permanganate Solution. ■ — In the rection given 
above we may consider that, as the molecule of K2Mn208 breaks 



ANALYSIS BY OXIDATION AND REDUCTION. 97 

up, three of the eight atoms of oxygen are required to form the 
basic oxids K2O and 2MnO (soluble in the acid as K2SO4 
and 2MnS04), while the remaining five atoms are liberated and 
constitute the active chemical agent whereby the oxalic acid is 
oxidized to CO2 and H2O. Hence to reduce this double molec- 
ular weight (316) to the hydrogen equivalent necessary for a 
normal solution, it is divided by 10 (five atoms of oxygen 
having a valence of 10). 

The Decinormal Solution may be made by dissolving 3.16 
grams of pure recrystallized and thoroughly dried crystals, if 
they can be obtained, in distilled water, and making the solu- 
tion up to 1000 c.c, or it ma)^ be standardized by titration with 
the N/10 oxalic acid previously prepared; in this case one 
would proceed as follows: 

Make a solution slightly stronger than the standard required, 
say about 3.5 grams of the ordinary pure crystals in a liter 
of water; with this fill a burette, place 10 c.c, measured from 
a pipette, of N/10 oxalic acid in an evaporating-dish or casserole, 
dilute with about 50 c.c. of water, add about 10 c.c. of dilute 
sulphuric acid, and heat the mixture nearly to the boiHng-point. 
Then titrate with the permanganate from the burette. The 
permanganate will at first be rapidly decolorized, but as the 
operation progresses the color fades more slowly till at last a 
faint permanent pink color indicates that the '^end point" has 
been reached. 

The temperature must be kept above 60° C. throughout the 
titration or the oxidation will take place too slowly, and an 
apparent end point will be obtained before the reaction is 
completed. 

If the solution turns muddy during the operation it is due 
to an insufficient amount of sulphuric acid and more should 
be added. The calculation is made as in the case of the N/10 
NaOH described on page 95. The standard permanganate 
should be preserved in full, well-stoppered bottles and kept 
in a dark place. 



98 VOLUMETRIC ANALYSIS. 

It is better to have the KMn04 solution made up a day or 
two before it is standardized, thereby oxidizing traces of am- 
monia, etc., which the water may contain. 

DETERMINATION OF PEROXID OF HYDROGEN. 

In determining the strength of peroxid use 1 c.c. of the 
sample measured as in the case of vinegar (which see), dilute 
with 50 c.c. of distilled water, add 10 c.c. of dilute sulphuric 
acid, and titrate with the permanganate in exactly the same 
manner as detailed in the preceding paragraph, the reaction in 
this case being as follows: 

2KMn04 + 5H2O2 + 3H2SO4 = K2SO4 + 2MnS04 + 5O2 + 8H2O. 

The aqueous solutions of peroxid on the market used as 
antiseptics contain about 3% absolute H2O2 and yield approxi- 
mately ten volumes of available oxygen; that is, 10 c.c. of solu- 
tion will yield 100 c.c. of oxygen. The calculation may be 
made to express strength of the peroxid in terms of percentage 
of absolute H2O2 by multiplying the number of cubic centimeters 
of N/10 KMn04 decolorized by 1 c.c. of solution by 0.17, or 
to express the strength in volumes of available oxygen by 
multiplying the number of cubic centimeters of solution by 0.56 
(more accurately 0.5594). 

DECINORMAL lODIN. 

A decinormal solution of iodin may be prepared by dis- 
solving 12.68 grams of pure iodin crystals in one hter of water 
by the aid of about 18 grams of pure potassium iodid. 

Iodin of sufficient purity may be obtained by carefully re- 
subliming selected and carefully dried crystals of so-called 
''chemically-pure" iodin. 

DECINORMAL SODIUM THIOSULPHATE. 

Na2S203 • 5H2O = molecular weight, 248.24. This solution may 
be made by weighing directly 24.824 grams of the pure crystal- 



ANALYSIS BY OXIDATION AND REDUCTION. 99 

lized salt, dissolving in water and diluting to 1000 c.c, or it 
may be standardized by titration with a decinormal iodin 
solution, the reaction being as follows: 

2Na2S203 + 2T = 2NaI + Na2S406. 

The indicator used is a very dilute starch paste which gives 
the characteristic blue color as soon as free iodin is in excess. 

By means of these two standard solutions (iodin and sodium 
thiosulphate) a variety of determinations may be made with 
great accuracy. Any substance which will liberate iodin from 
potassium iodid may be quantitated by adding an excess of 
the potassium salt and titrating the free iodin with thiosulphate 
solution, using starch paste as usual for an indicator. 

Peroxid of hydrogen may be thus determined as easily 
as by the permanganate method previously given. The process, 
being that of Kingzett, is given as follows by Sutton: 

Mix 10 c.c. of peroxid solution to be examined with about 
31 c.c. of dilute sulphuric acid (1-2) in a beaker, adding crystals 
of potassium iodid in sufficient quantity, and after standing 
five minutes titrating the liberated iodin with N/10 thiosul- 
phate and starch. The peroxid solution should not exceed 
the strength of two volumes; if stronger, it must be diluted 
proportionately before the analysis. 

In the case of a very weak solution it will be advisable to 
titrate with N/100 thiosulphate. 

1 c.c. N/10 thiosulphate = 0.0017 gram H2O2 or 0.0016 gram. 

VOLUMETRIC DETERMINATION OF ARSENIC. 

Mohr's method of oxidation with iodin is a practical one. 
The titration is made with N/10 iodin and starch as usual, 
except that the solution should be at first neutral and then 
about 20 c.c. of saturated solution of sodium bicarbonate 
should be added to every 0.1 gram of AS2O3 supposed to be 
in the unknown, thus giving a certain definite alkalinity. If 

LOf C. 



100 VOLUMETRIC ANALYSIS. 

the solution is acid, neutralize with sodium bicarbonate, then 
make alkahne with more bicarbonate as above. 

VOLUMETRIC DETERMINATION OF GOLD. 

While gold is usually determined quantitatively by assay 
in a dry way (page 104) it may be determined very accurately 
by titration Avith thiosulphate solution. Fatka (Chem. Zeit.) 
recommends the following process based upon the facts that 
a neutral solution of gold salt with potassium iodid will give 
a greenish precipitate. When an excess of potassium iodid 
is used no precipitate is formed, but a solution of Auls as AUKI4 
results. This is of a brown color and may be titrated with 
N/10 thiosulphate solution, when the following reaction takes 
place : 

AUKI4 + 2Na2S203 = AuKIs + 2NaI + Na2S406. 

Process: 10 c.c. of gold solution containing approximately 
2% of gold is treated with 4 grams of potassium iodid diluted 
to 100 c.c. with water and titrated with N/10 Na2S203 solu- 
tion, using starch as an indicator. 

Analysis by Precipitation. 

Because certain elements possess a selective affinity for 
other elements it is possible to determine many substances 
quantitatively by precipitation. That is, if silver nitrate is 
added to a mixture of a soluble chlorid and a chromate, the 
chlorin will combine first with the silver, forming AgCl, to 
the exclusion of the chromate. After the last trace of chlorin 
has been so combined, then the silver chromate will be formed, 
which is a salt with an intense red color; hence it is possible 
to determine the strength of solutions of soluble chlorids by 
titration with standard AgNOs, using potassium chromate as 
an indicator. This process is used in analysis of drinking- 
water, of saliva and of urine, but for each of these it is de- 
sirable to have solutions of special strength. 



ANALYSIS BY PRECIPITATION. 101 

A DECINORMAL SILVER SOLUTION 

may be made by dissolving 17 grams of pure crystallized 
AgNOa in a liter of distilled water, and with this a 

DECINORMAL SODIUM CHLORID SOLUTION 

may be prepared as follows: 

Weigh out 6 grams of the purest salt obtainable and dis- 
solve in approximately 1 Hter of distilled water. With a 
pipette measure 10 c.c. of this solution into a white porce- 
lain dish, dilute to about 50 c.c. with H2O, add two to five 
drops of neutral potassium chromate (K2Cr04) and add 
AgNOa from a burette till a faint pink color persists. 

The calculation and dilution is made exactly as described 
on page 95 in the preparation of a standard NaOH solution. 
The silver nitrate solution used to determine chlorin in urine 
is usually prepared of such a strength that 1 c.c. precipitates 
just 10 grams of sodium chlorid. This is equivalent to 
0.006065 gram of chlorin. A solution of this strength is pro- 
duced when 29.075 grams of pure, fused silver nitrate is dis- 
solved in sufficient distilled water to measure 1 liter of solu- 
tion. If chlorin is to be determined in drinking-water, it is 
usually necessary to concentrate the water at least 1/5 its 
bulk and then use not more than one or two drops of neutral chro- 
mate as indicator. The standard silver nitrate for this titra- 
tion should be very dilute. A convenient solution may be 
prepared by diluting the standard AgNOs for urine 1 to 10. 
In saliva the sample may be diluted with an equal volume 
of water and titrated the same as in the case of drinking-water. 
In all quantitative processes where silver chromate is used 
to determine the end point the solution must be practically 
neutral, as the formation of this salt is prevented by either 
acids or alkalis. 



102 VOLUMETRIC ANALYSIS. 



QUANTITATIVE ANALYSIS OF DENTAL ALLOYS 
CONTAINING Au, Sn, Ag, Cu, Zn. 

Weigh accurately 0.5 of a gram of alloy which has been 
reduced to fine filings and from which all particles of iron 
have been carefully removed by a magnet, transfer to a beaker 
and dissolve in 15 c.c. of strong HNO3 and 10 c.c. of H2O by 
aid of gentle heat. Evaporate on a water-bath till all nitric 
acid has been expelled. If the sample contains tin or gold^ 
complete solution will not be effected, but by watching the 
character of the sediment through the bottom of the beaker 
it is possible easily to determine when the alloy has been com- 
pletely disintegrated. 

After drying take up in H2O and filter immediately through 
a small ashless filter and wash with warm water eight or ten 
times, using about 5 c.c. each time and allowing the liquid to 
run through the paper before the next portion is added. Re- 
serve the residue on the paper for subsequent examination. 
Combine the filtrate and wash-water and make up to a definite 
volume, which may be 150 or 200 c.c, and titrate 10 c.c. for 
silver with N/10 NaCl solution, using potassium chromate as 
an indicator. 

Estimation of Copper. 

To 50 c.c. of the first filtrate (from which gold and tin 
alone have been separated) add HCl till silver is all precipi- 
tated. Filter, wash with warm water added in small portions 
eight to ten times. The filtrate with the wash-water, which 
should not exceed 100 c.c, is next warmed and H2S gas passed 
in until all second-group metals are thrown out. Filter and 
wash precipitate thoroughly, reserving the wash-water and the 
filtrate for the determination of zinc Dissolve the CuS in 
dilute HNO3. Wash paper thoroughly in warm water, add 
Na2C03 till the precipitate is nearly dissolved, then add 1 c.c 



QUANTITATIVE ANALYSIS OF DENTAL ALLOYS. 103 

of dilute NH4OH. Titrate, to complete disappearance of blue 
color, with KCN solution previously standardized after this 
same method against pure copper wire. A little practice is 
required in determining the end point to give the process any 
degree of accuracy. An excess of ammonia should be avoided, 
as it interferes with the accuracy of the end point. 

Copper also may be determined very easily by electrolysis 
of the faintly acid (H2SO4) solution, precipitating the Cu onto 
a platinum dish. The or(hnary 110-volt current employed for 
electric lighting may be used by introducing a resistance of 
seven to ten 16-c.p. lamps. After the copper has been entirely 
deposited the residual solution is drained out of the platinum 
dish, a little alcohol added, which is also drained out, and by 
setting fire to the last traces of alcohol the precipitated copper 
is dried and in condition to weigh. Care must be taken to 
avoid oxidation of the finely divided Cu; if it turns black too 
much heat has been used and partial oxidation has taken place, 
which will of course increase the weight. 

Estimation of Zinc. 

If zinc alone is left, as is usually the case, evaporate to 
dryness the solution previously reserved, dissolve in H2O, add 
a fairly strong solution of oxalic acid and an equal volume of 
strong alcohol. Allow to stand 15 to 30 minutes, filter, and 
wash with 70% alcohol till oxalic acid is removed, dry until 
the alcohol has disappeared, dissolve in dilute sulphuric acid, 
and titrate the solution with N/10 permanganate and calcu- 
late the zinc from the amount of oxalic acid found. 

Estimation of the Tin and Gold. 

The first residue containing the tin and gold is to be thor- 
oughly dried. If gold is present the residue is not white but 
purple in color. After drying remove the precipitate from the 
filter-paper, burn the paper in a tared porcelain crucible, add 
the bulk of the precipitate, ignite, cool, and weigh. If the ig- 



10-1 VOLUMETRIC ANALYSIS. 

nited residue consists only of stannic oxid the weight of tin 
may be obtained by multiplying the weight of the ash by 0.788. 
If gold is present the weight of the gold should be deducted 
from the total weight of residue before making the calculation 
for tin. 

The Assay of Gold and Silver in the Dry Way. 

It is often more convenient to determine gold and silver 
by the fire assay than by the volumetric methods previously 
given. This is accompHshed usually by fusion with an excess 
of lead and a borax flux. The mixture is kept at a high heat 
for upwards of thirty minutes, with a current of air passing over 
the surface of the molten metals. This serves to oxidize and 
carry away the baser metals, leaving the gold and silver with 
but a slight amount of lead, possibly a trace of copper and tin. 
The purification is completed by cupellation. When the 
traces of lead and other metals are absorbed by the cupel or 
are driven off as volatile oxids, the button of gold and silver 
is next cooled very slowly and carefully weighed. From this 
the silver may be dissolved by nitric acid unless the gold is 
in considerable excess, which would rarely be the case. If it 
should happen that the gold was present in sufficient quantity 
to prevent the solution of the silver in nitric acid a known 
weight of pure silver may be added in amount sufficient to 
increase the percentage of silver to 75 or over, fused, and 
then HNO3 will dissolve out all the silver, leaving the gold. 

The gold v/hich has resisted solution may be found as small 
black particles or grains in the bottom of the crucible. This 
should be carefully washed with distilled water by decantation, 
very carefully dried and brought to a red heat, which will give 
a button of pure gold. This may be weighed and the weight 
subtracted from the weight of gold and silver button pre- 
viously obtained. 



PART IV. 

MICROCHEMICAL ANALYSIS. 



The advantages of microchemistry are many, as claimed by 
its enthusiastic advocates, and there are two particulars in 
which these methods strongly recommend themselves to the 
dental practitioner: 1. Microchemical analysis deals with ex- 
ceedingly minute portions of matter, making the examination 
of very small particles of substance easily possible. 2. Three 
or four one-ounce ''drop-bottles'' and a few two-drachm vials 
will contain all necessary reagents, and in consequence three 
feet of bench room will furnish ample laboratory space. 

The principles of microchemical analysis are of course the 
same as for any analysis, but the processes employed are 
quite different and need some explanation. In microchemical 
analysis the production of crystals of characteristic form fur- 
nishes perhaps the most rapid method of detection of an un- 
known substance, and in this we are greatly aided by the use 
of polarized light, which not only helps in the differentiation 
of crystals but often makes it possible to see and distinguish 
small or transparent crystals which might otherwise escape 
notice altogether. 

Formation of crystals may be brought about in two ways: 
first, by precipitating insoluble crystalline salts by use of re- 
agents, as in ordinary quahtative analysis; second, by allowing 
salts to crystallize by spontaneous evaporation of the solvent. 

If the first method is to be employed it is essential to have 

105 



106 MICROCHEMICAL ANALYSIS. 

the dilution fairly constant in order to obtain crystals which 
shall be comparable with those obtained at other times or by 
other individuals. The tendency of strong solution is to give 
amorphous precipitates. Sometimes the precipitate will be 
amorphous when first thrown down, but upon standing will 
assume crystalline form. To secure the uniformity of results 
necessary to correct deductions the following method of pro- 
cedure should be exactly followed every time. 

First the reagent should be of uniform strength, usually 
1 or 2%; then place on a clean microscope-slide a small drop 
of the solution to be tested, and one of about equal size of 
the reagent to be used, and as close as possible to the drop 
of the " unknown " without touching it. Now bring the 
drops together by tapping the slide or with a small glass rod. 
If a precipitate forms immediately, cover loith a cover-glass 
(this must always be done) and examine with the microscope. 
If the precipitate is crystalline, note the form, and in any 
case, whether crystalline or not, repeat the test after diluting the 
unknown solution one-half. If the second test gives an amor- 
phous precipitate, or crystals of different shape from the first, 
continue the dilution ■ of the unknown till a point is reached 
when admixture with the drop of reagent gives no immediate 
precipitate, but one appearing in a few seconds' time (five 
to thirty). In this way we have produced the precipitate 
under standard conditions or as nearly such as is possible 
with unknown solutions. Until thoroughly familiar with the 
forms obtained by drying the various reagents, it is well to 
evaporate a small drop of the reagent alone, on the same slide 
on which a test is made, for the sake of subsequent comparisons. 

Filtration in microchemical examinations, when perhaps 
only a few drops of solution are to be had, may be effected 
in a very satisfactory manner and without appreciable loss 
by absorption as follows: 

Cut a filter-paper about 1 cm. wide and 6 long, double 
it and crease the middle so that it assumes the shape of an 



MICROCHEMICAL ANALYSIS. 107 

inverted V. Put the solution to be filtered in a small watch- 
glass placed at a slight elevation above a microscope slide; 
now place one " leg " of the strip of filter-paper in the watch- 
glass, allowing the end of the other to touch the slide. By 
capillary attraction the clear solution will follow over the 
bend in the strip of paper and a drop or two of perfectly clear 
filtrate will be found upon the slide suitable for the test. 

Evaporation of a solution is best effected on a small watch- 
glass held in the fingers and moved back and forth over a low 
Bunsen flame, or else placed over a water-bath. 

The purpose of the microchemical tests here outlined is 
not so much a method of general qualitative analysis, to which 
they are not suited, as it is a specific apphcation of well-known 
reactions to concrete examination of substances, the uses and 
probable composition of which are known, and the detail of 
the various tests wdll be given under classification furnished 
by the substances investigated. 

Our study may include alloys and amalgams, teeth, tartar, 
dental anaesthetics, cement, mouth-washes, antiseptics, disin- 
fectants, and sediments obtained from the saliva and from 
the urine. 

The following crystals are selected as among those most 
frequently met with in the analysis of the above substances 
or best suited for the study of microchemical processes, and 
the student should make each test here indicated and care- 
fully draw the crystals produced: 

1. Calcium oxalate from 2% H2C2O4 and CaCU solutions. 
(Plate III, Fig. 1). 

2. Cadmium oxalate from 2% H2C2O4 and CdS04 solutions 
(Plate III, Fig. 2). 

3. Strontium oxalate from 2% H2C2O4 and Sr(N03)2 solu- 
tions (Plate I, Fig. 3). 

4. Sodium oxalate by evaporation of aqueous solution, 
also by evaporation of urine containing Na2C204 (polarized 
light) (Plate III, Fig. 3). 



108 MICROCHEMICAL ANALYSIS. 

5. Urea oxalate from 2% H2C2O4 and urea solution (Plate 
III, Fig. 4). 

6. Ammonium-magnesium-phosphate from magnesium mix- 
ture * and sodium phosphate (Plate I, Fig. 4). 

7. Ammonium platinic chlorid (Plate I, Fig. 1). 

8. Ammonium phosphomolybdate from ammonium molyb- 
date and phosphate of sodium (Plate III, Fig. 5). 

9. Sodium urate by evaporation (polarized light) (Plate III, 
Fig. 6). 

10. Crystals formed from cocain and potassium perman- 
ganate. 

11. Crystals formed from carbolic acid and dilute bromine 
water (tribromphenol) (Plate IV, Fig. 1). 

12. Crystals formed from morphine solutions and ammo- 
nia (morphia) (Plate IV, Fig. 2). 

13. Crystals formed from morphine and Mamie's reagent 
(Plate IV, Fig. 3). 

14. Crystals formed from chloretone and sodium hypo- 
chlorite (Plate IV, Fig. 4). 

The list may be extended to include the crystals produced 
by various alkaloidal salts with the common reagents, also 
substances usually employed in the manufacture of the vari- 
ous dental preparations. 

" " LOCAL ANAESTHETICS. 

In considering the chemistry of local anaesthetics we may 
divide them into two classes as follows: 

1st. Those of definite or well-known composition, and 

2d. Preparations of a proprietary nature, the composition 
of which is always problematical. 

In the first class will be found cocain, eucain, tropacocain, 
acoin, ethyl chlorid, etc., which will be later alphabetically 

* Magnesium mixture as used in urine analysis to precipitate phosphates con- 
tains MgCla, (or MgSO,), NH,C1 and NH.OH. 



LOCAL ANESTHETICS, 109 

considered. The second class contains a large number of 
preparations of all degrees of value, among them some of 
exceeding merit and largely used, others of doubtful worth, 
some worthless if not dangerous. Many of the preparations 
of this class contain cocain as the anicsthetic, and frcniuently 
a little nitroglycerine as a cardiac stinmlant to counteract 
the depressant effect of the alkaloid. Carbolic acid and oil 
of clove are also frec^uently used. 

Many of the constituents of this class of anesthetics may 
readily be identified by the processes of microchemical analysis 
to which previous reference has been made, others may be 
detected by special tests, some of which are included in the 
following list of substances which have been extended to include 
a considerable number of preparations of common occurrence. 

Acoin, asynthetic compound (chemically diparanisyl-mono- 

/(NC6H40CH3)2\ \ 

phenetyl-guanidine hydrochlorid, C HCl ) sol- 

\(NC6H40C2H5)/ / 

uble in both alcohol and water. Strongly antiseptic and a 
valuable anaesthetic, especially in conjunction with cocain. 
Acoin should be used only in solution and this should be kept 
in a dark place. 

Adrenalin, a valuable haemostatic and frequently used in con- 
junction with dental anaesthetics, is the active principle of the 
suprarenal gland or capsule. It occurs as very small white 
crystals which are not very stable and only slightly soluble 
in water, hence the article is usually sold in solution with 
sodium chlorid, according to the following formula taken from 
a commercial sample: 

Adrenalin chlorid, 1 part. 

Normal sodium chlorid solution (with 0.5% chloretone), 
1000 parts. This solution is usually diluted with the normal 
(0.6%) salt solution. According to the Druggists' Circular, 
preparations similar to the above are also marketed under the 
names of adrenol, adnephrin, hemostatin, supraredaHn, etc. 



110 MICROCHEMICAL ANALYSIS. 

Anesthol, or i^nsesthol, is a mixture of ethyl chlorid and 
methyl chlorid, used as a local dental ansesthetic. The name 
is also applied to a general anaesthetic given by inhalation and 
consisting of a mixture of ethyl chlorid, chloroform, and ether. 

Argyol, a compound of silver with albumin, soluble in 
water and recommended in place of ordinary silver nitrate 
solution. It contains 30% metallic silver. 

Atropine, an alkaloid obtained from belladonna, usually 
used as the sulphate, (Ci7H23N03)2H2S04; the alkaloid is only 
sparingly soluble in water but the sulphate is easily soluble, 
dissolving in about half a part of water at ordinary tempera- 
ture. A 1% solution is said to produce complete insensi- 
bihty of the nerves in cases in which an artificial tooth is inserted 
in a living root. (U. S. D., page 249.) 

Tests. — Atropine may be separated from a local anaesthetic 
by first rendering the mixture alkaline with ammonia and 
shaking with chloroform. Upon evaporation of the chloro- 
form solution on a watch-glass the resulting residue may be 
tested by adding a drop or two of sulphuric acid and a trace of 
potassium bichromate and a little water. The odor of bitter 
almonds is produced. Or a more conclusive test is to convert 
the alkaloid, which has been dissolved out with the chloro- 
form, into a salt by the addition of a few drops of acetic acid, 
evaporating to complete dryness, taking up in a few drops of 
distilled water and placing one or two drops of this solution 
in the eye of a cat; when, if atropine is present, a dilation of 
the pupil occurs in fifteen minutes to an hour and a half's time, 
according to amount present. 

Borax. — Sodium tetraborate, Na2B407,, is used in antiseptic 
solutions and may be detected by evaporating a little of the 
solution to dryness, adding a little HCl. Evaporate to dryness 
a second time, then add a very dilute HCl solution containing 
tincture turmeric. Upon drying this mixture a beautiful pink 
color appears. If much organic matter is present it may be 
burned off in the Bunsen flame before the addition of any acid. 



LOCAL ANESTHETICS. lU 

Carbolic Acid.— Phenol, CelisOH, obtained from the de- 
structive distillation of coal-tar. A light oily liquid of specific 
gravity of 0.94-0.99. Carbolic acid is usually obtained as a 
white crystalline mass soluble in 15-20 parts of water. The 
pure acid turns pink with age, but does not suffer deterioration 
on account of this change of color. The addition of from 
5-8 per cent of water will cause liquefaction of the crystals 
and the preparation becomes permanently liquid. It is easily 
soluble in glycerine and strong solutions may thus be prepared. 
Carbolic acid is sometimes added to local anaesthetics with the 
intent of rendering the solution sterile, but as shown by Dr. 
Endelman (Dental Cosmos, Vol. 45, page 44) it would be 
necessary in order to prevent the development of micro-organisms 
to add the acid in proportion that would render the solution 
unfit for hypodermic purposes. 

Tests. — Phenol may be detected in the majority of prepara- 
tions by the adcUtion of bromin- water, which gives white crys- 
tals of tribromphenol (see Plate IV, Fig. 1). 

Chloral Hydrate, CCI3CPIO.H2O, a crystalline solid com- 
posed of trichloraldehyde or chloral with one molecule of water 
(U.S. P.). Easily soluble in water, may become with alcohol 
a chloral alcoholate comparatively insoluble in water. 

Tests, — Chloral may be detected by adding to the suspected 
mixture a few cubic centimeters of fairly strong alcoholic 
solution of KOH or NaOH with one drop of aniline oil and 
heating, when isobenzonitril is produced, which has a pecu- 
liarly disagreeable and characteristic odor. This test is given 
by chloroform, which is produced by heating chloral hydrate 
with caustic alkaU. If more than traces of chloral are present 
this latter reaction may be a sufficient test. 

Chloretone, CCl3COH(CH3)2, is the commercial name of 
acetone-chloroform or tertiary trichlorbutyl alcohol. Made 
from chloroform, acetone, and an alkali, and occurs as small 
white crystals, with taste and odor like camphor. It is dis- 
solved by alchool and glycerine and to sHght extent by water. 



112 MICROCHEMICAL ANALYSIS. 

Tests. — A convenient microchemical test for chloretone 
devised by Mr. Niles, Harvard Dental School, '06, consists^ 
simply of treatment with a solution of hypochlorite of sodium. 
A precipitate is at once formed of a coarsely branching charac- 
ter which thus far seems to be characteristic of chloretone 
solutions (Plate IV, Fig. 4). 

Chloroform, trichlormethan, CHCI3, prepared by action of 
chlorinated lime on acetone. Chloroform is a heavy colorless 
liquid with a specific gravity of 1.490 at 15° C. It is a very 
volatile solvent for gutta-percha, caoutchouc, many vegetable 
balsams, camphor, iodin, bromin, and chlorin; it also dissolves, 
sulphur and phosphorus to a limited extent. 

Tests. — It may be detected by its odor, heated, or by the* 
isobenzonitril test, to which reference has been made under 
chloral hydrate. 

Cocain is the alkaloid obtained from erythroxylon coca. 
The hydrochlorate C17H21NO4HCI is the salt most usually^ 
employed. This is easily soluble in water and very largely 
used as dental anaesthetics in 1 or 2% solution. 

Tests. — Cocain solutions respond to the usual alkaloidal 
reagents. With 1% solution potassium permanganate gives, 
pink plates in form resembling cholesterin (Plate IV, Fig. 5)^ 
Dilute cocain solution with picric acid gives a yellow pre- 
cipitate which becomes crystalline on standing. Quite char- 
acteristic crystals also may be obtained from dilute cocain 
solutions and stannous chlorid in the presence of free HCI 
(Plate IV, Fig. 6). 

Creosote. — A mixture of phenols derived from the destruc- 
tive distillation of wood tar. It is a heavy oily liquid act- 
ing when pure as an escharotic. It is analogous in many 
respects to carbolic acid and may be used for similar pur- 
poses. To distinguish between creosote and carbolic acid, boil 
with nitric acid until red fumes are no longer given off. 
Carbolic acid will give yellow crystalline deposit; creosote 
will not. An alcoholic solution of creosote is colored emerald 



LOCAL ANESTHETICS. 113 

green by an alcoholic solution ferric chloricl. Phenol is col- 
ored blue. 

Cresol is the next higher homologue to phenol, having a 
formula C3H4CH3OH, boiling at 198° C. It is largely used, 
usually together with allied compounds from coal-tar, as anti- 
septic and disinfectant solutions. 

Ektogan. — Peroxid of zinc, Zn02, designed for external 
use (London, July 9, 1904). 

Ethyl Chlorid, monochlorethan, C2H5CI. This is a gaseous 
substance at ordinary temperature, but when used as a dental 
anaesthetic it is compressed to a colorless liquid which has 
a specific gravity 0.918 at 8° C, is highly inflammable and 
usually sold in sealed glass tubes of 10-30 grams each. 

/?-Eucain is the hydrochlorate of benzoylvinyldiacetone- 
alkamine, and occurs as a white, neutral powder, soluble in 
about 30 parts of cold water. It is used like cocain as a 
local anaesthetic, and is claimed to be less toxic, and sterilizable 
by boiling without fear of decomposition. It is applied mostly 
in 1 to 5% solutions, which are conveniently prepared in a 
test-tube with boihng water. It is also marketed in the form 
of IJ- and 5-grain tablets. (Druggists' Circular.) 

Eucain Lactate. — " Eucain lactate is used in 2 to 5% 
solution as a local anaesthetic in ophthalmic and dental prac- 
tice and in 10 to 15% solution when used in the nose or ear.'' 
(Review of American Chemical Research, page 97, 1905.) 

Formaline, Formal, Formine, etc., are commercial names 
for a 40% aqueous solution of formaldehyde, HCHO, pre- 
pared by the partial oxidation of methyl alcohol. Formaline 
is a powerful disinfectant very generally used. (For test see 
page 141, Exp. 14.) 

Glycerine is a triatomic alcohol, C3H5(OH)3, a colorless 
liquid of syrupy consistence and sweetish taste, a specific gravity 
1.250 at 15° C. It is easily soluble in either water or alcohol. 

Tests. — Upon heating strongly, it is decomposed, giving 
off odors of acrolein, which fact is usually sufficient for its 



114 MICROCHEMICAL ANALYSIS. 

identification. A further test may be made by moistening a 
borax bead on a platinum wire with the suspected solution 
(after concentration) and holding in a non-luminous flame, 
to which it will give a deep-green color which does not per- 
sist. Glycerine when present is apt to interfere with char- 
acteristic crystallization of many precipitates. 

Heroin is a diacetic ester of morphine. It is usually ob- 
tained as the hydrochlorid and occurs as a white powder, 
soluble in two parts of water. Its action is similar to that 
of morphine; it answers to the usual tests for morphine, but 
may be distinguished from it by the fact that it will yield 
acetic ether upon heating with alcohol and sulphuric acid. 

Hopogan (also known as biogen) is a peroxid of magnesium, 
Mg02, recommended as a non-poisonous and non-astringent 
intestinal germicide. 

Hydrogen Peroxid, or dioxid, H2O2, is, when pure, a syrupy 
liquid without odor or color. It is obtained under various 
trade names in aqueous solution containing about 3% and 
yielding upon decomposition about 10 volumes of oxygen 
gas. It is used also as an escharotic in etherial solutions con- 
taining 25 to 50% H2O2. Peroxid solutions may be con- 
centrated by heat without decomposition if kept perfectly 
free from dirt or traces of organic matter. It is readily pre- 
pared by treatment of metaUic peroxids, as Ba02 with dilute 
acids. 

Ba02 + H2SO4 = BaS04 + H2O2 
or BaOs + H2O + CO2 = BaCOs + H2O2. 

This latter reaction has the advantage of producing an insolu- 
ble barium compound and at the same time introducing no 
objectional acid. The peroxid of sodium, calcium, magnesium, 
and zinc may also be used; Zn02, however, is comparatively 
expensive and used in powder form as an antiseptic dressing 
rather than as a source of H2O2. Na202 is valuable as a 
bleaching agent, as for this purpose an alkaline solution is re- 



LQCAL AN/ESTHETICS. 115 

quired and the solution of Na202 in water produces both alkali 
and H2O2 according to the following reaction: 

Na202 + 2H2O = 2NaOH + H2O2. 

Sodium perborate (page 117), also sold as euzone, is a 
powder advertised to produce H2O2 in water. Commercial 
• H2O2 solutions are usually acid in reaction, as such solutions 
are more stable than if neutral or alkaline. 

Menthol is the stearopten obtained from the oil of pepper- 
mint. It is a volatile crystalhne substance having a formula 
C6H9OHCH3C3H7. Menthol is but slightly soluble in water 
but freely soluble in alcohol, ether, chloroform, or glacial acetic 
acid. The presence of menthol may usually be detected by 
its odor. If the odor should be suggestive but not distinctive 
it is well to place a Uttle of the substance on a filter-paper, 
rub it between the thumb and finger, thereby obtaining a 
''fractional evaporation," when the more easily volatile sub- 
stance will pass off first, thus producing a partial separation of 
substances. 

Mercuric Chlorid, corrosive sublimate, HgCU, soluble in 
about 16 parts of water and 3 parts alcohol. A powerful anti- 
septic, in aqueous solution 1/1000 to 1/5000, and occasionally 
used in mouth- washes. 

Tests. — A drop of the suspected solution with a trace of 
potassium iodid will give a red precipitate of mercuric iodid 
soluble in excess of either reagent. With Ume-water or fixed 
alkaUne hydroxids a black precipitate is produced. A drop of 
mercurial solution placed on a bright copper plate will leave 
a tarnished spot due to the reduction of the mercuric salt and 
subsequent amalgamation of the metal. 

Methethyl. — Ethyl chlorid mixed with a Uttle methyl chlorid 
and chloroform is said to be the composition of a local anaes- 
thetic sold under the name of methethyl (U. S. D.). 

Methyl Chlorid, CH3CI, is a colorless gas which condenses to 
a liquid at 23° C. Methyl chlorid is easily soluble in alcohol, 



116 MICROCHEMICAL ANALYSIS. 

somewhat in water, and is used in a similar manner to ethyl 
chlorid. 

Morphine, C17H19NO3, alkaloid from opium. It is usually 
used as a sulphate, hydrochlorate, or acetate. The alkaloid 
itself is insoluble in water, its salts are easily soluble. 

Morphine may be separated from solutions containing it by 
making the solution alkaline with ammonia and shaking out 
the precipitated alkaloid with warm amyl alcohol. Upon 
evaporation of the alcohol the residue may be tested with 
Frohde's reagent (sodium molybdate in strong sulphuric acid). 
The color obtained should be a violet, changing usually to 
brown; a pure blue color is not distinctive for morphine. If 
the morphine solution is of sufficient strength the addition of 
ammonia will produce minute crystals of the alkaloid as shown 
on Plate III, Fig. 5. Dental anaesthetics containing morphine 
will give precipitates with the usual alkaloidal reagents. 
Marme's reagent (Cdl2) gives crystals represented on Plate IV, 
Fig. 3. 

Nitroglycerine, C3H5(N03)3, is used as a cardiac stimulant 
in alcohoHc solution, the U. S. P. Spiritus Glonoini, containing 
1% by weight of the substance. 

Oil of Clove, oil of Gaultheria, and other essential oils may 
be detected by the same process of fractional evaporation as 
suggested under menthol. In testing for the presence of any 
substance by its odor, it is usually necessary to make a com- 
parative test on known samples using the same methods. 

Orthoform, C6ll30H(NH2)COOCH3, methylparaamido- 
metaoxybenzoate, used as an anaesthetic and antiseptic, is 
without odor, color, or taste, is shghtly soluble in water and 
easily soluble in alcohol or ether. 

Phenol.— See Carbolic Acid. 

Potassium Hydroxid, KOH, gives an alkaline reaction to 
Utmus paper and may 'be detected by the ordinary methods 
of inorganic analysis. 

Rhigolene is a light inflammable liquid from petroleum. 



LOCAL ANESTHETICS. 117 

boiling at about 1S° C, used as a spray for the production of 
low temperature, similarly to methyl or ethyl chlorid. It is 
readily inflammable and the vapor mixed with certain propor- 
tions of air is explosive. It should be kept in a cool place. 

Silver Nitrate, AgNOs, crystallizes in colorless plates without 
water of crystallization; used as an antiseptic, disinfectant, 
or escharotic. It is freely soluble in water and may be detected 
by the ordinary methods of quaUtative analysis (page 6). 

Sodium Chlorid, NaCl, is a constituent of very many prepa- 
rations designed to be used hypodermically. Experience has 
proved the value of such addition; perhaps tlie reason for its 
desirability is given by Dr. G. Mahe, of Paris, in the Dental 
Cosmos for September, 1903, in the statement that sodium 
chlorid added in excess to a toxic substance diminishes its 
toxicity by one half, and this has been demonstrated particu- 
larly with cocain. 

Sodium Perborate, a powder said to be the composition 
NaBOs -41120, which will furnish 10% of available oxygen 
and produce II2O2 with water; very stable and recommended 
as a bleach-powder. 

Sodium perborate may be made * by thoroughly mixing 
78 grams Na20 and 248 grams of crystallized H3BO3 and stirring 
the mixture gradually into 2 liters of cold H2O. The sodium 
perborate, Na2B4O8 + 10H2O, is formed spontaneously and 
settles out from the solution as a white crystalline powder. 
Its solubility is increased by addition of weak organic acids, 
citric or tartaric. 

Sodium Peroxid, Na20. — A white powder easily soluble in 
water, usually with evolution of more or less oxygen and forma- 
tion of hydrogen dioxid. 

Somnoform. — A general anaesthetic administered in manner 
similar to chloroform; introduced by Dr. Holland, of Bordeaux; 
consists of 60% ethyl chlorid, 35% ethyl bromid, and 5% 
methyl bromid. (Dental Cosmos, ^^ol. XLVII, page 236.) 

* Dental Cosmos, Nov. 1905, page 1381. 



118 MICROCHEMICAL ANALYSIS. 

Tannic Acid, or tannin, sometimes called gallotannic acid, 
is an astringent organic acid obtained from nutgalls. It may 
be obtained as crystals carrying 2 moleucles of water, 
HC14H9O92H2O. Tannic acid is a white or slightly yellowish 
soHd sohible in about one part of water or 0.6 part alcohoL 
It is used as an alkaloidal precipitate, also in astringent washes. 
It may be detected by the addition of ferric solutions which 
form with it a black tannate of iron of the nature of ink. 

Thymol, C10H14O, a phenol, occurring in volatile oils of thy- 
mus vulgaris (Line). Melts at 44° C; sparingly soluble in 
water, easily in alcohol and ether. 

Tests. — It may usually be detected by its odor or by a 
smaU crystal dissolved in 1 c.c. of glacial acetic acid, then 
if 6 drops of sulphuric acid and 1 drop of nitric acid be added, 
the liquid will assume a deep bluish-green color. (U.S.D.) 

Trichloracetic Acid occurs as deliquescent crystals, readily 
soluble in water. Distils at 195° C. and is a powerful caustic. 
Dilute solutions are recommended for treatment of pyorrhoea. 

Tropa-cocain is an alkaloid originally isolated by Giesel 
from the leaves of small-leaved coca-plant of Java and intro- 
duced by Arthur P. Chadbourne, Harvard Medical School. 
Used hypodermically in normal salt solution. It is probably 
superior to cocain, but rather more expensive. It is obtained 
as an oil which, when quite dry, solidifies in radiating crystals, 
melting at 49° C. It is easily soluble in alcohol. 

TEETH AND TARTAR. 

The chemical examination of teeth and tartar, while coming 
more properly under the head of physiological chemistry, will 
be considered in part in this place, as the tests made, especially 
on tartar, are practically all microchemical. The composition 
of the cement is practically that of true bone, the dentine 
and enamel differing principally in the proportion of organic 
matter which they contain. In all of these the presence of 



TEETH AND TARTAR. 119 

lime, phosphoric acid, carbonic acid, and traces of magnesium 
and calcium fluorid may be demonstrated. The tartar con- 
tains a greater proportion of carbonic acid, less calcium phos- 
phate, and nmch less organic matter than the teeth, taken as 
a whole, or than dentine, but about the same as enamel. 
According to Berzelius, sodium chlorid and sodium carbonate 
may also be found. 

The composition of the different parts of the tooth sub- 
stance has been given as follows: 

\llften ^^^- Ca3(P04)2. MgHPO,. CaCOj. 

Dentine 23.2 76.8 70.3 4.3 2.2 

Cement 32.9 67.1 60.7 1.2 2.9 

Enamel 3.1 96.9 90.5 traces 2.2 

Also traces of magnesium carbonate, calcium sulphate, fiuorids, 
and chlorids. An increase in the percentage of calcium phos- 
phate or fluorid increases the hardness of the tooth, while an 
increase of calcium carbonate decreases the hardness. 

In tartar, potassium sulphocyanate, ferric phosphate, 
sulphites, and uric acid have been found as additional chem- 
ical constituents, while after the solution of the mineral mat- 
ter the presence of epithelium cells, mucus, and the leptothrix 
may be demonstrated by the microscope. 

According to Vergness, Du tartre dentaire, quoted by Gamgee, 
the tartar from incisor teeth and that from molars show decided 
difference in their content of iron and calcium phosphates, 
the analysis being as follows: 

Tartar of Incisors. Tartar of Molars. 

Calcium phosphate 63 . 88-62 .56 55 . 11-62 . 12 

Calcium carbonate 8 . 48- 8 . 12 7 . 36- 8 . 01 

Phosphate of iron 2 . 72- 0. 82 12 . 74- 4 . 01 

Silica 0.21-0.21 0.37-0.38 

Alkaline salts 0.21-0.14 0.37-0.31 

Organic matter 24.99-27.98 24.40-24.01 

Tartar from patients with pyorrhoea alveolaris has been 
found to contain oxalates and urates, not necessarily together, 
but often one or the other. The deficient oxidation and high 



120 MICROCHEMICAL ANALYSIS. 

acidity usually occurring in such cases is conducive to the pro- 
duction of large amounts of oxahc or uric acids (most gen- 
erally the latter) whether these substances have etiological 
relations to pyorrhoea or not. 

Lactic and other organic acids have been found in minute 
quantities in tartar, but these as well as the quahtative tests 
for urates will be considered more in detail under the Chemis- 
try of Saliva. 

Analysis of Teeth and Tartar. 

The substance for analysis should be reduced to a moder- 
ately fine powder by crushing in a mortar and a fair sample 
of the whole taken for each test. 

Moisture may be detected by the closed tube test (page 53) 
and may be determined by accurately weighing out 1 gram 
of the substance in a counterpoised platinum dish or crucible 
and drying at 100° C. to constant weight. 

Inorganic Matter may be determined by careful ignition 
of dried substance; raise the temperature slowly till full red 
heat is reached; cool in a desiccator and weigh. 

Organic Matter may be obtained by difference. 

Lactates and other organic acids may be detected by care- 
ful crystallization and examination with the micropolariscope. 

The several inorganic constituents may be demonstrated 
as follows: 

Phosphoric Acid. — Dissolve a little of the powdered sub- 
stance in dilute HNO3; then to a few drops of the clear solu- 
tion add an excess of ammonium molybdate in nitric acid. 
A yellow crystalline precipitate of ammonium phosphomolyb- 
date will separate. Avoid heating above 60° C, as the ammo- 
nium molybdate may decompose and precipitate a yellow 
oxid of molybdenum. 

Carbonic Acid may be detected by liberation of CO2 and 
passing the gas into lime-water as described on page 43 or 
v/ith closed tube and drop of baryta-water, page 53. 



TEETH AND TARTAR. 121 

Chlorin may be detected in the dilute nitric acid solution 
by the usual silver nitrate test. 

Calcium and Magnesium may be separated and identified 
by the usual methods of analysis in the presence of phosphates. 

Test for calcium and magnesium as follows: Add to the 
HCl solution (1) an excess of ammonia. Calcium phosphate 
and magnesium phosphate are precipitated, white. Filter, 
and to the filtrate add ammonium oxalate; a white precipi- 
tate shows lime, not as phosphate. Wash the precipitate 
produced by NH4OH, dissolve in dilute HCl, and add Fe2Cl6 
carefully till a drop of the solution gives, when mixed with 
a drop of NH4OH, a yellowish precipitate. Nearly neutralize 
with Na2C03 and add BaCOs, which precipitates ferric phos- 
phate. Filter, heat the filtrate, precipitate the barium with 
dilute sulphuric acid, and filter. From the filtrate calcium 
is precipitated as white calcium oxalate by making alkaline 
with NH4OH and adding (NH4)2C204 as long as a precipitate 
is formed. Filter and add to the filtrate sodium phosphate, 
which precipitates magnesium as ammonio-magnesium phos- 
phate, white. 



PAET V. 

ORGANIC CHEMISTRY. 



SEC. I— THE HYDROCARBONS AND SUBSTITUTION 
PRODUCTS. 

Our work up to this point has been confined to inorganic 
chemistry (excepting a few microchemical tests for organic 
substances). We are now to enter upon the study of oiganic 
or as some define it '^carbon " chemistry, and the chemistry 
of the carbon compounds is a domain so vast that its mag- 
nitude almost overwhehns us. 

We shall touch but lightly some of the subdivisions of the 
subject and take up a little organic chemistry proper, a little 
physiological chemistry, a little pathological chemistry, and 
from it all pick out such facts as may help us to a better under- 
standing of the problems of dentistr}^ 

The carbon compounds contain the elements of C and H, 
and when these two only are present they are hydrocarbons. 
They more frequently contain C, H, and 0, and when the H 
and are present in the proportions in which they occur in 
water, the compound is a carbohydrate (with exceptions). 

In the chemistry of the animal body the majority of sub- 
stances which we meet contain C, H, 0, and N and often in 
addition S or P. Many other elements, notably the halogens, 
and often the metals, may be found in organic compounds. 

122 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS. 123 

The (question of its composition is then the first one pre- 
senting itself in the consideration of an organic substance. 

Qualitative Tests. 

Carbon. — The presence of this element may be shown by 
the " carbonization " obtained in the prehminary test on 
platinum foil (page 52). 

Hydrogen shows itself by the production of moisture in 
these same tests. 

Nitrogen may be indicated by the preliminary test or may 
not. It may be detected with certainty by either of the fol- 
lowing methods: 

(a) Conversion into a cyanogen compound; 
(6) Conversion into free ammonia. 

(a) A small piece of thoroughly dried albumen is placed in 
a matrass described on page 10, together with a little metallic 
potassium, and heated to redness for a few minutes. (MetaUic 
sodium will work as well in most cases.) An alkah cyanide 
is formed which may be dissolved in water after breaking 
the tube, and by addition of a little yellow ammonium sulphid 
and evaporation to dryness on a water-bath will be changed 
to sulphocyanate, NH4CNS. If the dry residue is taken up 
with dilute HCl, filtered, and tested with a drop of ferric chlorid 
solution, the presence of the sulphocyanate is at once shown 
by the red color produced. 

(h) Most nitrogenous substances may be made to evolve 
ammonia-gas by simply heating in a test-tube with several 
times its bulk of soda-lime. Test for NH3 by moistened red 
litmus paper or odor. (This test is known as that of Wohler, 
also of Will and Varrentrap.) 

The Kjeldahl or moist combustion process is much employed 
as a quantitative method but may be used qualitatively as 
follows: The substance is heated in an ignition-tube with 
concentrated sulphuric acid till a clear (not necessarily color- 
less) solution is obtained. The mixture is cooled, diluted \^^th 



124 ORGANIC CHEMISTRY 

water, an excess of caustic soda added, and heat applied when 
NH3 is evolved, which may be detected by Utmus paper or 
odor as above. 

Sulphur and Phosphorus are first completely oxidized 
either by fusion of the substance with alkali nitrate and car- 
bonate, or by treatment in the wet way with fuming HNO3 
or mixture of KCIO3 and HCl. The resulting sulphate or phos- 
phate is detected by the usual qualitative methods (page 44). 

A sulphur test may also be made by heating the substance 
with a little concentrated NaOH in the test-tube. A little 
sodium sulphid will thus be formed which may be detected 
by dropping onto a bright silver coin or by testing with lead 
acetate solution. 

Halogens. — CI, Br, and I cannot be detected in organic 
combinations by the ordinary qualitative test with AgNOs 
and dilute NHO3, but must first be converted into correspond- 
ing inorganic haloid salts. This may be done by heating the 
organic substance strongly with pure lime, when calcium 
chlorid, bromid, etc., will be formed, which may be dissolved 
in water and tested in the usual way. 

A test for chlorin or iodin may also be made by heating 
with copper oxid on a platinum wire in the Bunsen flame, chlorin 
giving first a blue then a green color to the flame. Iodin 
gives a green only (Beilstein). 

Exp. 1. Test for presence of C, H, and S in dried albumen. 

Exp. 2. Test for S by the caustic soda test. 

Exp. 3. Test for P in casein precipitated from milk. 

Exp. 4. Make tests for the halogens with a few drops of 
chloroform. 

The Hydrocarbons. 

The hydrocarbons are organic compounds of carbon and 
hydrogen only. The simplest of these being marsh-gas or 
methane (CH4). The molecule of this substance consists 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS. 125 

of a single carbon atom with each of its four points of atonriic 
attraction (valence) satisfied by an atom of hydrogen. 

H H 

\n/ 
/\ 

H H 

If one of these four atoms of H is replaced by a chlorin 
atom, for instance, we have a substitution product. Its formula 
will be CH3CI, its name monochlormethan or methyl chlorid. 
If two molecules of methyl chlorid arc brought together and 
the CI removed by metallic sodium the residual molecules 
(methyl radicals) will unite, forming a new hydrocarbon, as 
follows : 

2CH3CI + Na2 = 2NaCl + C2H6 (ethan) . 

By a similar reaction we may form the third member of 
the series, CsHg (propan), from ethyl chlorid (C2H5CI) and 
sodium; the fourth member, butan, C4H10, from propyl chlorid, 
etc., etc. A tabulated list of the first five compounds of this 
series will plainly show their chemical relationship: 

CH4, methan or methyl hydrid (CH3H). 

C2H6, ethan or ethyl hydrid (C2H5H). 

CaHg, propan or propyl hydrid (C3H7H). 

C4H10, butan or butyl hydrid (C4H9H). 

C5H12, pentan or amyl hydrid (C5H11H). 

Note that the various members of this series differ from 
one another by CH2; that is, each higher compound contains 
one carbon atom and two hydrogen atoms more than its prede- 
cessor. This holds true through the series, and the compounds 
of this or any such series are termed homologues and the series 
homologous series. Note further that any member of this 
series (which is known as the paraffin series) may be represented 
by the general formula CnH2n+2- This likewise holds true 
throughout the series, and a compound having sixty carbon 



126 ORGANIC CHEMISTRY. 

atoms will have a formula of C60H122. The first four hydro- 
carbons of this series are gaseous at ordinary temperatures; 
from C5H12 to about C16H34 the hydrocarbons are liquid; 
from C16H34 (melting at about 18°) up they are solids. 

Isomers. — When two or more compounds are of exactly 
the same molecular composition in regard to numbers and 
kind of atoms, they are isomeric substances or isomers. 

Thus we may have a normal butan represented graph- 
HHHH 
ically by H-C-C-C-C-H (C4H10), then we may have an iso- 

HHHH 
meric or isobutan represented by 





H 




H 1 H 




\i/ 


H 

1 


/ 


1 

:— c- 
1 

H 


-c/ H 
H \C— H 




\ 




H 



also C4H10, but having different physical and chemical proper- 
ties from the normal compound. The greater the number of 
carbon atoms in the molecule the more numerous the possible 
isomers. 

Polymers. — When one compound has a formula which may 
be regarded as a multiple of another it is said to be a polymer 
of it; thus paraform, a white crystalHne soHd, (CH20)3, is a 
polymeric form of the gaseous formaldehyde CH2O. 

The hydrocarbons of the paraffin series are known as straight 
chain or aliphatic hydrocarbons, their graphic formulae con- 

I I I I 
sistine; of '^ chains " of carbon atoms, as butan, -C-C-C-C-, in 

_ I I ! I 

distinction from the closed-chain or cyclic compounds as rep- 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS. 127 

resented by the 'M^enzole-riiig " (page IGl) carbon nucleus with 
the C atoms united in a continuous closed chain or " cycle." 

The paraffins are called saturated hydrocarbons because 
they are incapable of forming addition products by absorption 
of CI, for instance, without first giving off an equivalent num- 
ber of atoms of H. This is because of the complete '' satu- 
ration " or union of every carbon '' bond " with some other 
atom* Paraffin wax and mineral oil are mixtures of saturated 
hydrocarbons and resist chemical action even of strong nitric 
acid or sulphuric acid. 

If two carbon atoms are united by a double bond, as in 
H H 

yC^C\^ (C2H4), chlorin may be added directly by the 
H H 

breaking of the double bond, forming ethylene chlorid, C2H4CI2. 

Note that the formula of ethylene does not conform to the 
general formula of the paraffins (CNH2N+2), but is the first 
member of the new series of '^ unsaturated " hydrocarbons; 
the olefin or ethylene series with a general formula of CnH2n. 

The hydrocarbons of this series take their names from 
corresponding members of the paraffin series, with " ene " as 
a distinguishing termination — ethylene, C2H4, propylene, CjHe, 
butylene, C5H10, etc. They are unimportant in dental or 
physiological chemistry. Some of the higher oxygenated 
compounds of this class are, however, of great importance, as 
olein, which is a constituent of vegetable and animal fats and 
oils. 

A third series of the straight chain hydrocarbons is the 
acetylene series; these are triple bonded, and of course unsatu- 
rated, with a general formula of CnH2n-2. 

The only members of this series of special interest are, first, 
acetylene, H — C=C — H, (C2H2), made from calcium carbid 

* Notice that while addition products of saturated hydrocarbon cannot be 
formed, substitution products are easily possible. See page 125. 



128 ORGANIC CHEMISTRY. 

and water. It is poisonous, combining directly with the haemo- 
globin of the blood, has a disagreeable odor, and is inflammable; 
second, allylene, C3H4, derivatives of which occur in onions^ 
garlic, mustard-oil, etc. 

Haloid Derivatives of the Paraffins. 

These are substitution products. Among the compounds 
of this class used in dental medicine the following may he 
mentioned : 

Methyl Chlorid, CH3CI, may be made from methyl alcohol,, 
zinc chlorid, and hydrochloric acid. It is a colorless gas, con- 
densing to a hquid at 23° C; used as a spray in producing; 
local anaesthesia (page 115). 

Ethyl Chlorid, C2H5CI, chlorethyl, may be made by dis- 
tillation of a mixture of alcohol and hydrochloric acid and 
purification of the distillate. It is extremely inflammable, 
boils at 12° C, and is used as a local anaesthetic in similar 
manner to methyl chlorid. Its higher boiling-point make& 
it the more convenient of the two preparations (see page 113)» 

Ethyl Bromid, C2H5Br, prepared from alcohol, sulphuric 
acid, and potassium bromid. It is a heavy colorless Hquid,. 
does not burn, and has been used to considerable extent as a 
general anaesthetic. 

Methylene Chlorid, CH2CI2, has been used as a general 
anaesthetic, usually mixed with more or less chloroform and 
alcohol. 

Methyl lodid, CH3I, is a heavy liquid, with pleasant odor,, 
boiling-point 43° C; has been used somewhat as a vesicant. 

Iodoform, HCI3, tri-iodomethan, is a much-used and very 
valuable antiseptic. It is a hght-yellow crystalline powder 
with characteristic persistent odor (Plate V, Fig. 1). 

Iodoform may be made by heating in a retort two parts 
of potassium carbonate, two of iodin, one of strong alcohol, 
and five of water, till the mixture is colorless. 

Iodoform is also produced from action of above reagents. 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS. 129 

with acetone in place of alcohol. This reaction is a very deli- 
cate one and advantage is taken of it in testing for acetone 
in saliva, which see. 

Bromoform, CIIBrs, tribroni-nicthan, prepared from bromin 
and a solution of alcoholic potash. Its properties are similar 
to those of chloroform, but it is more poisonous. 

Chloroform, CIICI3, trichlormethan, is a general anesthetic 
prepared by distilling a mixture of chlorinated Ume and acetone. 
Alcohol and water were formerly used in place of acetone (see 
Exp. 10, p. 130). While it is not regarded as inflammable, its 
heated vapor can be made to burn with a greenish flame. 

Methyl Chloroform, CH3CCI3, formed by replacing the H 
atom of chloroform by a methyl group, CH3, has been used 
as an anaesthetic. 

E:tperiments loith the Hydrocarbons and Haloid Derivations. 

Exp. 5. Charge an ignition-tube with dry '' marsh-gas 
mixture " found on side shelf (consisting of NaC2H302, NaOH^ 
and Ca02H2). Fit with a delivery-tube and collect two small 
bottles of the gas over water. 

NaC2H302 + NaOH = CH4 + Na2C03 . 

Test the inflammability of this gas. Notice the odor. 

Exp. 6. Mix carefully in a test-tube 2 c.c. of alcohol and 
8 c.c. of strong sulphuric acid. Heat gently and notice odor 
of gas. Fit a bent glass tube to the test-tube and collect over 
water a test-tube full of the gas. To this apply a flame. Note 
the color of the burning gas. 

C2H5OH— H20 = C2H4. 

Exp. 7. In a small generator (see model) place a few 
small pieces of calcium carbide (CaC2), add strong alcohol 
through the funnel tube till the lower end of the tube is 
"sealed." Now add very slowly a little water till a brisk 



130 ORGANIC CHEMISTRY. 

evolution of gas is obtained. Collect over water two or three 
test-tubes full of the gas. Acetylene. 

Test with a lighted splinter. Note odor of gas cautiously, 
as it is poisonous when inhaled in quantity. 

CaC2+2H20 = Ca(OH)2 + C2H2. 

Exp. 8. Conduct a little of the acetylene gas into an am- 
moniacal cuprous chlorid solution. What is the red pre- 
cipitate? 

Exp. 9. If the evolution of gas has not been interrupted 
the delivery- tube may be replaced by a short tube drawn out 
to a fine point and the gas ignited. Note color of flame. If 
it smokes badl};^, explain the reason for it. 

Exp. 10. Place in a test-tube a httle bleaching-powder, 
cover with strong alcohol and heat the mixture to boiling. 
Notice carefully the odor of the vapor produced and compare 
with a little chloroform (CHCI3) from side shelf. 

4C2H5OH + 8Ca(C10)2 = 2CHCI3 + 3Ca(CH02)2 + SCaCb + 8H2O. 

(Formate of Ca) 

Exp. 11. Place in a test-tube about 1 gram of crystallized 
carbonate of sodium, about half as much iodin and 1 or 2 c.c. 
of alcohol. Now add 10 or 15 c.c. of H2O and keep the mix- 
ture at moderate heat (not boihng) till the color of the iodin 
is di-scharged. Allow to cool; collect on a small filter-paper 
some of the yellow crystals which have been formed and examine 
under the microscope. What are the crystals? Explain 
their relation to marsh-gas. 



SECTION II.— ALCOHOL. 

If we substitute for one of the hydrogen atoms of methane 
a hydroxyl group (OH) we shall produce the first of a series 
of alcohols, several of which will claim our attention. Alcohols 
may be considered as compounds containing an alkyl radical 



ALCOHOL. 131 

and a distinctive alcohol group, and are primary, secondary, 
or tertiary according to relative position of the group. (See 
page 132.) 

Alcohols are mono-, di-, tri-atomic, etc., according to the 
number of alcohol groups they contain. 

CH2OH 1 



CHOH \ , glycerine, is thus a triatomic alcohol, while 

CH2OH . 
mannite, CH2OH-CHOH-CHOH-CHOH-CHOH-CH2OH, or 
C6Hs(OH)6, is a hexatomic alcohol. 

Methyl Alcohol, CH3OH, (H-CH2OH),* ^Yood spirit, carbinol, 
is a product of the destructive distillation of wood or can be 
made synthetically from methane. It is a colorless, inflam- 
mable Hquid, with a gravity of 0.802 at 15° C, with solvent 
properties similar to ordinary alcohol, and boils at 66°. 

Ethyl Alcohol, C2H5OH, (CH3-CH2OH), methyl carbinol, 
grain alcohol, or ordinary alcohol is made by fermentation of 
solutions of various carbohydrates and purified by distilla- 
tion. Carbon dioxid is evolved as follows: 

CeHi 2O6 = 2C2H5OH + 2CO2. 

95% alcohol has a specific gravity 0.8164, boils at about 
78° C, dissolves many inorganic salts, vegetables, waxes, resins 
(not gums), oils, etc. Miscible with water, ether, or chloroform. 

Amyl Alcohol, C5H11OH, (C4H9-CH2OH), isobutyl carbinol, 
a colorless, oily liquid with a specific gravity of 0.818. It 
boils at about 130° C. and burns with a bluish flame. 

Fusel-oil, or potato spirit, consists of amyl alcohol carrying 
traces of various other alcohols as impurities. 

Amyl alcohol is a valuable solvent and is largely used in 
the manufacture of artificial fruit flavors, banana essence, 
and the like. 

* Note that CH^OH is the "alcohol group" peculiar to this class of alcohols. 



132 ORGANIC CHEMISTRY. 

The alcohols just considered are all primary alcohols; that 
is, the -OH group has been introduced into the hydrocarbon 
in place of an H of a -CH3 group, leaving a characteristic 
grouping for this class of compounds, -CH2OH. 

The hydro xyl derivatives (alcohols) of isopentan are well 
suited to illustrate the three (primary, secondary, and tertiary) 
characteristic alcohol groupings. 

CH3V 

^CH-CH2-CH3 is isopentan 
CH3/ 

and by introducing the OH group (hydroxyl) into the CH3 
group there is formed a primary amyl alcohol, 

CH3V 

>CH-CH2-CH20H, or isobutyl carbinol, 

and the primary alcohol grouping is -CH2OH. By introducing 
hydroxyl (OH) into the CH2 group we should have -CHOH- 
as a characteristic combination in secondary alcohols, 

CH3V 

)>CH-CH0H-CH3, methylisopropyl carbinol; 

and lastly, by putting the OH in place of the H of the CH group 
of the hydrocarbon, we should have (CH3)2 = COH-CH2-CH3, 
a tertiary alcohol with the group =COH as its characteristic. 

Oxidation of the Alcohols. 

Aldehyds. 

The first step in the oxidation of an alcohol consists not 
in the addition of oxygen but in the withdrawal of hydrogen; 
thus the oxidation of methyl alcohol produces formaldehyd 
(CH2O) and water. 

CH3OH + O-CH2O + H2O. 



ALCOHOL. 133 

Aldehyds may be considered compounds containing an 

H H 

/ I 

alkyl radical and a distinctive group, -C ; thus CHO is for- 

\ 

maldehyd, CH3, in acetaldehyd, etc (compare Alcohol, page 

I 

CHO 
131). 

Formaldehyd coagulates albumen and hardens gelatine; 
when used as a preservative it renders the proteids tougher 
and less digestible. 

Formaldehyd polymerizes, producing the paraform or para- 
formaldehyd of trade, trioxymethylene, with a probable for- 
ula of (CH20)3. It also forms one lower polymer (CH20)2 and 
at least one higher, formose, a substance allied to glucose. 

Acetaldehyd, aldehyd, CH3-CHO or C2H4O, the aldehyd 
from ethyl alcohol, may be made by addition of H2SO4 to a 
mixture of alcohol and bichromate of potassium. It is a 
colorless, inflammable liquid with pungent etherial odor and 
boils at 22° C. 

Paraldehyd, (C2H40)3, a polymer of acetic aldehyd, is a 
*' colorless liquid with a strong pungent odor, soluble in 8.5 
parts of water at 15° C, miscible in all proportions with alcohol, 
ether, and fixed or volatile oils." (U. S. P.) It is a valuable 
hypnotic. 

Chloral, CCI3CHO, trichloraldehyd, is an oily liquid formed 
by action of dry CI gas on pure alcohol; soluble in ether and 
chloroform, boiling at 94° C. to 98° C, and forming, with a 
molecule of H2O chloral hydrate, CCI3CHO.H2O, a crystalline 
solid, and this is the '^chloral " of the pharmacopoeia (see page 

111). 

Chloral hydrate is decomposed by caustic soda or potassa 
with liberation of chloroform (see Exp. 20, p. 142) : 

CCl3-CHO + KOH = CHCl3 + KCOOH (potassium formate). 



134 ORGANIC CHEMISTRY, 

Upon warming a drop or two of aniline oil an excess of 
alcoholic potash chloral hydrate forms, first, chloroform, then 
penyhsocyanid, CeHsNC, the persistent disagreeable odor of 
which furnishes a delicate test for chloroform or chloral (see 
Exp. 21, p. 142). By using CHCI3 as the reagent in place of 
the aniline, the same reaction becomes a test for aniline or 
organic compounds, from which aniline may be produced by 
heating with alcoholic potash as acetanihd. Other aldehyds 
from hexatomic alcohols are dextrose (glucose) and galactose. 
They are represented by the formula CH20H-(CHOH)4-CHO, 
and will be considered more fully in a subsequent lecture. 

Ketones. 

The oxidation of secondary alcohols (page 132) will not 
yield aldehyds, but a class of substances known as ketones: 

(CH3)2-CH -CHOH-CH3 + = (CH3)2-CH-C : O-CH3 + H2O, 

A secondary alcohol. Methyl isopropyl ketone. 

Methyl isopropyl carbinol. 

or CH3-CHOH-CH3 + = CH3-CO-CH3 + H2O. 

Isopropyl alcohol. Dimethyl ketone. 

The converse of each of these reactions is possible, and by 
reduction of a ketone wdth nascent H (sodium amalgam) the 
secondary alcohol will be formed: 

CH3-CO-CH3 + H = CH3-CHOH-CH3. 

Acetone. Isopropyl alcohol. 

Likewise primary alcohols may be produced by the reduc- 



tion of aldehyds 



CH3-CHO + H2 = CH3-CH2OH. 

Acetaldehyd. Ethyl alcohol. 

Note that the grouping peculiar to ketone is = CO. 

Acetone, or dimethylketone, CH3-CO-CH3, a colorless liquid 
of peculiar odor, boils at 56° C. and is made commercially 
by the dry distillation of acetate of lime. 



ETHERS. 135 

It occurs in the blood and urine of patients suffering from 
advanced diabetes. According to von Noorden the acetone 
found in the blood is formed by an intracellular process and in- 
dicates an acid auto-intoxication and an insufficient utilization 
of carbohydrates. Acetone may be found in the saliva, and 
that (in the experience of the author) sometimes when it 
cannot be found in the urine (for test, see Acetone under Saliva 
and Urine). 

Another ketone of interest is h^vulose, fruit-sugar, 
CH20H-CHOIi-CHOH-CHOH-CO-CH20H, which with glu- 
cose will be studied later. 

While the oxidation of a primary alcohol will produce an 
aldehyd and the oxidation of a secondary alcohol will produce 
a ketone, the tertiary alcohol, by action of an oxidizing agent, 
is split into two new carbon compounds, that is, the chain is 
broken and simpler ketones and acids are formed. 

SECTION III.— ETHERS. 

Ethers may be regarded as oxids of the hydrocarbon radi- 

C2H5\ 

cals, as ^0, or as anhydrids of the monatomic alcohols, 

C2H5^ 

H2O having been removed from two molecules of the alcohol: 
2C2H50H-H20 = (C2H5)20. 

Ethers may be simple, mixed, or compound. The simple 
ether is illustrated above by the formula for ordinary or ethyl 
ether, w^iere two radicals of the same kind are united by an 
atom of oxygen. 

In a mixed ether these radicals wdll be of different kinds, 
as, for example, CH3-O-C2H5, methyl-ethyl ether. 

The compound ethers are compounds of alcohol radicals 
with acid radicals, that is, the salts of alcohol radicals. The 
acid may be either organic or inorganic; thus we have nitric 



136 ORGANIC CHEMISTRY. 

ether, ethyl nitrate, C2H5NO3, and we have acetic ether, ethyl 
acetate, C2H5C2H3O2. The compound ethers are often called 
esters and form a large and important class of organic com- 
pounds. 

Methyl Ether. — Methyl oxid, (CH3)20, also known as formic 
ether, is isomeric with ordinary alcohol, and may be made in 
a manner similar to that used in the production of ethyl ether 
(q. v.). At ordinary temperature it is a gas, but liquefies at 
—20° C. (Bernthsen). It has been used as a general anaesthetic, 
and the anaesthesia is said to be profound and quickly pro- 
duced (U. S. D. from A. J. P., Sept., 1870). 

Methyl-ethyl Ether. — This name, besides indicating a 
definite compound as referred to in the preceding paragraph, 
has been apphed to a mixture of methyl ether and ethyl ether, 
used for purposes of general anaesthesia. 

Methylene Ether. — A name applied to a mixture of methyl- 
ene dichlorid and ethyl ether, used as an anaesthetic, but 
has been found unsafe (U. S. D.). 

Ethyl Ether.— Ethyl oxid, (C2H5)20, consisting of 96% by 
weight of the " aether " of the pharmacopoeia (the other 4% 
being alcohol and a little water). Ether is a general anaesthetic, 
widely used. It is made by the action of sulphuric acid on 
ethyl alcohol, and from this fact has been known as sulphuric 
ether, but this name is, of course, incorrectly used, sulphuric 
ether being properly an ethyl sulphate (€2115)2804. 

In the preparation of ether, sulphuric acid may be mixed 
with rather more than its own bulk of alcohol, the mixture 
heated to a temperature of 130° to 138° C. in a suitable retort 
or still, the distillate (ether) being collected in a cold receiver. 

The reaction takes place in two steps, as follows : One mole- 
cule of acid and one of alcohol react to form ethyl sulphuric 
acid (ethyl acid sulphate) and H2O, H2S04 + C2H50H = 
C2H.5HS04-f H2O. Then the ethyl sulphuric acid reacts with 
a second molecule of alcohol to form ether and sulphuric acid, 
C2H5HSO4 + C2H5OH = (C2H5)20.+ H2SO4. Thus the sulphuric 



ETHERS. 137 

acid, from two molecules of alcohol, has produced one mole- 
cule of ether and is in condition to repeat the process, having 
suffered itself only to the extent of adulteration with one mole- 
cule of water. In accordance with this theoretic formation 
of ether by simple dehydration of alcohol by H2SO4 provision 
is made for a continuous process, by the introduction of a 
constant supply of fresh alcohol into the retort during the 
distillation, and so regulated that the total bulk of liquid is 
neither increased nor diminished. The product is then puri- 
fied, freed from water and traces of acid by redistillation over 
a mixture of lime and calcium chlorid. Ether, according to 
to the U. S. P. requirements, is '^ a transparent, colorless, 
mobile liquid with characteristic odor and a burning and sweet- 
ish taste"; specific gravity of 0.725 to 0.728 at 15° C. and 
boiling at about 37° C. 

It is readily inflammable, and this fact, together with its 
easy volatility, makes it necessary to use considerable care 
when handling it. Absolute ether boils between 34° and 35° C. 

The action of sulphuric acid upon alcohol needs careful 
regulation; and there are three other possible products in 
addition to the ethyl oxid already considered. These are, 
first, ethyl sulphuric acid, C2H5HSO4; second, ethyl sulphate 
(02115)2804, these being respectively the acid and neutral 
ethyl esters of H2SO4; third, the hydrocarbon ethylene, C2H4. 
This latter compound is the first of the ethylene series of 
hydrocarbons with the general formula CnH2n, and contain- 

ing "double-bonded" carbon atoms, >C = C<' or 

W \H 

CH2 = CH-CH3. These are unsaturated hydrocarbons (see 
page 127). Ethylene is produced by the action of an excess 
of concentrated H2SO4, which abstracts H2O from each mole- 
cule of alcohol (C2H50H-H20 = C2H4), whereas in the prepara- 
tion of ether the more dilute acid abstracts H2O from two 
C2H5OH. 



138 ORGANIC CHEMISTRY. 



Compound Ethers or Esters. 

One of the most important of this class of compounds, 
from a dental standpoint, is the benzoyl-ecgonine methyl 

( C5H7 
ester or cocain, CH3N ^ | . While of 

( CH.C7H5O2.CH2-CO2CH3 
considerable interest, the elucidation of the exact chemical 
relationship of this compound to tropacocain, etc., is beyond 
the scope of this work. 

Another methyl ester of much simpler chemical composition 
is methyl sahcylate, CH4-Cn-C00CH3. 

SaHcylic acid is CH4-OH-COOH (oxybenzoic acid), and 
its methyl ester constitutes the methyl sahcylate of the U. S. P. 
It is identical with the volatile oil of betula and with 90% 
of the oil of gaultheria (wintergreen). This latter oil is much 
used as a flavor in dental preparations, tooth-washes, powders, 
etc. 

Ethyl Acetate, CH3-COO.C2H5, formed by heating ethyl 
alcohol, sulphuric acid, and acetate of sodium. This reaction 
constitutes a qualitative test for acetic acid or acetates, the 
odor of the ester being sufficiently characteristic to furnish 
a delicate test (page 49). 

The acetic ether of the U.S. P. is " a liquid composed of 
about 98.5% of ethyl acetate and 1.5% alcohol." 

Ethyl Butyrate, CH3-CH2-CH2-COOC2H5. This ester dis- 
solved in 10 parts of alcohol forms pineapple essence. It 
may be made in a manner similar to the preparation of ethyl 
acetate, i.e., by heating together alcohol, butyric acid, and 
concentrated sulphuric acid. The production of the ester is 
likewise used as a qualitative test for the presence of the acid, 
and employed in the examination of gastric contents as follows : 
'^ Heat 10 c.c. of contents with 5 c.c. of strong sulphuric acid 
and 4 c.c. of 95% alcohol: odor of pineapple indicates butyric 
acid." (Hewes.) 



ETHERS. 139 

Ethyl Nitrite, C2H5NO2, may be made by heating sodium 
nitrite with concentrated sulphuric acid and alcohol, also by 
the reduction of nitric acid by copper in presence of alcohol 
and sulphuric acid. The ethyl nitrite is distilled, and must 
be collected in a receiver surrounded by a freezing mixture of 
ice and salt. Pure ethyl nitrite boils aL 1S° C. and has a gravity 
of 0.900. An alcoholic solution constitutes sweet spirits of 
nitre, the spiritus setheris nitrosi of the U. S. P. 

This preparation should, according to Dr. E. R. Squibb, 
contain 4.5% ethyl nitrite. 

Amyl Acetate and Amyl Butyrate may be obtained by heat- 
ing the respective acids with amyl alcohol (C5H11OH) and 
strong sulphuric acid. These esters may also be used in detect- 
ing the presence of the acid, amyl alcohol being used in place 
of ordinary alcohol. Amyl acetate gives the odor of pears,, 
amyl butyrate that of bananas. 

Amyl nitrite, C5H11NO2, a compound used in medicine 
to a considerable extent, usually administered by inhalation. 
The U. S. P. preparation contains about 80% of amyl nitrite. 
It is very soluble and inflammable. 

The Fats are esters of glyceryl, C3H5, also called tritenyl, 
propenyl, etc. This radical forms with hydroxyl (OH) the 
propenyl alcohol, C3H5(OH)3, which is ordinary gylcerin or 
glycerol. 

Glyceryl butyrate or butyrin, CH3-(CH2)2-COOC3H5, con- 
stitutes (together with smaller quantities of the glyceryl esters 
of capric, caproic, and caprylic acids) about 7% of butter- 
fat. These esters are readily saponified by treatment with 
alcohoHc potash; then, by decomposition of the potassium 
salts with H2SO4, the acids, being volatile, may be separated 
by distillation. The amount of volatile fat acids thus obtained 
is a valuable test for the genuineness of the butter. 

Glyceryl Palmitate, C3H5(Ci6H3 162)3 tripalmitin, glyceryl 
stearate, C3H5(Ci3H3302)3, tristearin, and glyceryl oleate, 
C3H5(C4sH3302)3, tnoleiu,— these in varying proportions make 



140 ORGANIC CHEMISTRY. 

up the greater part of animal and vegetable fats and 
oils. 

The prefix '' tri " is used because the " mono " and ^^ di " 
compounds, as monopalmatin, C3H5(OH)2-Ci6H3i02, etc., are 
possible and may be prepared by synthesis. Triolein is liquid 
at ordinary temperature, soUdifies at -6° C, is a ''double- 
bonded " compound, hence forms addition- products with the 
halogens as stearin and palmitin cannot do, they being " satu- 
rated hydrocarbons." 

The amount of chlorin or bromin which a fat or oil can 
thus absorb is an nidex of the proportions of fatty acids of this 
class contained in them, and hence becomes a valuable method 
of identification. Olive-oil and lard-oil contain large amounts 
of olein. 

Tripalmitin melts at 66° C, is usually obtained from palm- 
oil. Tristearin melts at 72^ C, occurs with palmitin and olein 
in beef-fat, mutton-tallow, etc., the consistence of the fat being 
dependent upon the proportions of the constituent esters. 

The fats, stearin for example, may be split into glycerol 
and fatty acid by steam under pressure as follows: 

C3H5(Ci8H3502)3 +3H2O = C3H5(OH)3 + 3HC18H35O2. 

A partial result of this nature is brought about by the fat- 
splitting enzyme (lipase) of the pancreatic juice (see Steapsin). 
Saponification of the fats by caustic alkali takes place as 
follows : 

C3H5(Ci8H3502)3 + 3K0H = C3H5(OH)3 + 3KC18H35O2. 

The potassium salts of the fatty acids constitute the soft 
soaps, while the sodium salts are in general the hard soaps. 
The '' salting-out " process in soap manufacture brings about 
a double decomposition resulting in the production of ordi- 
nary soap. 



ETHERS. HI 

Experiments ivith Alcohols, Aldehyds, and Ethers, 

Exp. 12. To about 75 c.c. of a 10% glucose solution add 
a little yeast, and allow to stand for twenty-four hours at a 
temperature of about 37° C; then distil by means of gentle 
heat 10 or 15 c.c., and test distillate for alcohol by iodoform 
test, as given on page 130, Exp. 11. The production of CO2 
may also be demonstrated if the gases evolved during the 
fermentation are passed into clear lime-water: 

CeHi 2O6 - 2C2II5OH + 2CO2. 

Exp. 13. Formaldehyd may be made by the partial oxi- 
dation of methyl alcohol (wood-spirit) by passing the vapor 
of the alcohol mixed with air slowly over a red-hot spiral of 
platinum wire. AVith a little of the solution so prepared, or 
with the 40% solution known as " formaline," make the follow- 
ing test: 

Exp. 14. Mix about 1 c.c. of solution to be tested with 
four or five times its volume of milk in a test-tube. Care- 
fully underlay the mixture with commercial sulphuric acid 
of a specific gravity of 1.80. At the point of contact of the 
two layers of liquid a violet-colored ring indicates the pres- 
ence of formaldehyd. It is necessary that the sulphuric acid 
should contain a trace of iron: this the commercial acid usu- 
ally does. It is also undesirable that the acid should be stronger 
than of 1.80 specific gravity; for, if it is, a reddish-brown ring 
may be formed, due to partial carbonization of the casein. 

Exp. 15. To about 5 c.c. of a strong aqueous solution of 
potassium dichromate add a little sulphuric acid, then a few 
cubic centimeters of alcohol, and notice the odor of acetaldehyd 
produced by oxidation of the alcohol. Note also the reduction 
of the dichromate to Cr2 (804)3, as follows: 

KaCrsOT + 4H2SO4 + 3C2H5OH = 

K2SO4 + Cr2(S04)3 + 3C2H4O + 7H2O. 



142 ORGANIC CHEMISTRY. 

Exp. 16. Apply to dilute solution of both formic and 
acetic aldehyd ToUen's test for aldehyd, which is made as fol- 
lows : Into a clean test-tube which has been rinsed with caustic 
soda solution place 5 c.c. of a reagent made by dissolving 
3 grams silver nitrate in 30 c.c. of ammonia-water and adding 
3 c.c. of sodium hydroxid. Add the solution to be tested when 
the silver is reduced, forming a metallic mirror on the inner 
surface of the test-tube. 

Exp. 17. Into a large test-tube put a little alcohol and 
about half its volume of strong H2SO4. Warm gently and 
notice the odor. 

Ether is formed by two reactions. First, C2H5OH + H2SO4 
= C2H5HS04 + H20. Then the ethyl-hydrogen sulphate 
(C2H5HSO4) is acted upon by a second molecule of H2SO4, 
as follows: 

C2H5HSO4 + C2H5OH = (C2H5)20 + H2SO4. 

Exp. 18. The production of compound ethers may be dem- 
onstrated by the test for acetic acid forming ethyl acetate, 
page 49, or by the following experiment used to detect butyric 
acid in gastric contents: 

Exp. 19. Mix in a test-tube 5 c.c. of a dilute (i%) solu- 
tion of butyric acid with an equal volume of strong H2SO4 
and as much strong alcohol. Heat gently and note the odor 
of ethylbutyrate (pineapples). 

Exp. 20. To about 5 c.c. of an aqueous solution of chloral 
hydrate add a few cubic centimeters of strong NaOH solution 
and boil. Note odor of chloroform. 

Exp. 21. Isobenzonitril test for chloral or chloroform: 
Place a few drops of a dilute chloral hydrate solution (or a 
small drop of chloroform) in a test-tube, add 5 c.c. of an alco- 
holic solution of alkali hydrate * (NaOH or KOH) and one drop 

* If alcoholic potash or soda is not at hand, the test may be performed with 
5 c.c. of alcohol and 1 or 2 c.c. of a 40% aqueous solution of NaOH. 



ORGANIC ACIDS. 143 

only of fresh aniline oil. Heat till the mixture just Ijcgins 
to boil and note the odor of the nitril. 



SECTION IV. ORGANIC ACIDS. 

If the oxidation of an alcohol is carried beyond the for- 
mation of aldehyd or ketone, i.e., if the aldehyd or ketone 
be oxidized, an organic acid results. The first atom of oxygen 
involved in this process does not become a constituent part 
of the new molecule, ])ut simply withdraws hydrogen from 
the old (the alcohol); but the second atom of oxygen attaches 
itself to the molecule and does become a part of the new sub- 
stance (the acid) : 

CH3 CH3 CH3 CH3 

I +0= I +H2O I +0= I 

CH2OH CHO CHO COOH 

Alcohol. Aldehyd. Acetic aldehyd. Acetic acid. 

The group -COOH is known as carboxyl and is the char- 
acteristic grouping of the acids. The H of the carboxyl differs 
from the other atoms of H in the molecule in that it is united 
to oxygen rather than to carbon, and constitutes the basic 
or replaceable H of the acid; hence acetic acid is monobasic, 
and the only possible salt of potassium, for instance, is 
CH3-COOK. 

The basicity of the acid depends on the number of carboxyl 
groups it contains. 

Among the monobasic acids of the fatty or paraffin series 
which we will study are the following: 

Representative Fatty Acids. 

H.COOH = formic acid or hydrogen formate; 
CH3.C00H = acetic acid or hydrogen acetate; 
C2H5.COOH = propionic acid or hydrogen proprionate; 
C3H7COOH = butyric acid or hydrogen butyrate; 



144 



ORGANIC CHEMISTRY. 



C4H9COOH = valerianic acid or hydrogen valerianate j 
Ci5H3iCOOH = palmitic acid or hydrogen palmitate; 
Ci7H35COOH = Stearic acid or hydrogen stearate. 

Of the Acrylic Acid Series 
C17H33COOH, or oleic acid, is the only one of interest. 

Dibasic Acids. 



COOH 
COOH 

Oxalic acid. 



COOH 

CH2 

COOH 

Malonic acid. 



COOH 
CH2 
CH2 
COOH 

Succinic acid. 



Oxy acids. 

Hydroxy acids, or alcohol acids, contain hydroxyl in place 
of one or more hydrogen atoms of the fatty acids. Thus we- 
may consider 

Carbonic acid as hydroxyformic acid, HO-COOH ; 

CH2OH 

Gly colic acid as hydroxy acetic acid, I ; 

C2H4OH 
Lactic acid as hydroxypropionic acid, I ; 

Malic acid (from apples) as hydroxysuccinic acid,. 
CHOH-COOH 

CH2-COOH 

CHOH-COOH 

Tartaric acid is dihydroxy succinic acid, I 

^ -^ CHOH-COOH 

Citric acid, from lemons, limes, etc., is in a class by itself. It 

is a tribasic acid (has three carboxyl groups and one hydroxyl) ; 

the formula is C3H40H-(COOH)3. 

Formic Acid (H.COOH), originally distilled from the bodies 

of ants (formica), is a colorless, very soluble Hquid. It may also 



ORGANIC ACIDS. 145 

be made by passing CO over hot KOH and by heating glycerine 
and oxaHc acid. 

Acetic Acid, CH3COOH, is obtained commercially by the 
oxidation of ethyl alcohol. It is the acid of vinegar, which, 
accorcHng to Massachusetts law, should contain 4\%. Glacial 
acetic acid is a commercial name of the acid containing 1% 
or less of water: it is a colorless solid at a temperature below 
15° C. The U. S. P. acetic acid contains only 36% (by weight) 
of the pure acid. 

Either one, two, or all three of the hydrogen atoms of the 
CH3 group may be replaced by chlorin, forming respectively 
the mono-, di-, or trichloracetic acids, the trichloracetic acid 
being used to a considerable extent in dentistry (page 118). 

Butyric Acid, C3H7COOH, occurs as a product of fermenta- 
tion of butter, or other animal fat containing butyrin; also 
from the decomposition of lactic acid, two molecules of lactic 
acid furnishing one of butyric acid, 2CO2 and 2H2. It is an 
occasional constituent of the gastric contents, and may be 
detected by formation of the ethyl ester (page 138). The 
pure acid is a heavy, colorless liquid with characteristic odor, 
soluble in H2O in any proportion. See page 139 for the glyceryl 
ester of butyric acid (butyrin); also for stearic and palmitic 
acids. 

Oleic Acid, closely allied to palmitic and stearic, does not 
belong to the saturated hydrocarbons but is a double-bonded 
acid, hence an unsaturated compound (page 127). 

Dibasic acids contain two carboxyl groups. These are 

referable to, and in many cases may be formed from, the di- 

CH2OH 
atomic alcohols. Thus glycol, I , upon oxidation yields 

CH2OH 

CH2OH COOH 

glycollic acid, ' ^^tt ' ^^^ ^^^^^^ ^^^^' COOH ' 

Oxalic acid, which may be considered as a type of the di- 
basic acids, occurs as small, colorless crystals (four- or six-sided 



146 ORGANIC CHEMISTRY. 

prisms), containing two molecules of water of crystallization, 
(II2C2O4.2H2O); it is but slightly efflorescent, and, if care- 
fully crystallized, is suitable for the preparation of standard 
acid solution. Salts of oxahc acid occur in many plants; 
the acid potassium oxalate, ^' salt of sorrel," is found in com- 
mon red sorrel (Rumex acetora) and in wood sorrel (Oxalis 
acetocella). Oxalic acid in various combinations, often with 
lime, is widely distributed in articles of vegetable diet, par- 
ticularly tomatoes, rhubarb, spinach, and asparagus; grapes, 
apples, and cabbage also carry oxalates, but in smaller amounts. 

The source of oxalates in the system is twofold, — the ingested 
oxalates and those produced by oxidation, incident to meta- 
bolism, the exact nature of which has not been clearly demon- 
strated (see Calcium and Sodium Oxalates, under Urine and 
Saliva), 

Oxalic acid was previously made commercially by the 
action of strong nitric acid on starch or sugar; it is now pre- 
pared by heating cellulose (in form of sawdust) with a mix- 
ture of KOH and NaOH, precipitating the acid as CaC204, 
and decomposing the salt by H2SO4. The acid is then puri- 
fied by repeated crystallization. 

Succinic Acid, COOH(CH2)2-COOH, which may be obtained 
by the saponification of ethylene cyanid, C2H4(CN)2, is a 
dibasic acid containing four carbon atoms. It is a constituent 
of some transudates and cyst fluids. It occurs- in the spleen 
and thyroid gland, and has been found in sweat, and, accord- 
ing to some authorities, in the urine (Hammarsten). 

OXYACIDS. 

Several acids of this class are of importance to the student 
of dentistry. 

Lactic Acid. — Oxypropionic acid, or i * -ethylidene lactic 
acid, CH3-CHOII-COOH, is ordinary lactic acid produced by 

* Optically inactive. 



ORGANIC ACIDS. 147 

fermentation of milk, sugar, etc. It occurs in the gastric juice 
and in contents of the intestine, '' particularly during a diet 
rich in carbohydrates," possibly in nmscle and brain tissue 
(Foster). 

Sarcolactic or paralactic acid, d * -ethylidene lactic acid, 
occurs in meat extract. The presence of this acid causes the 
acid reaction of dead nmscle, possibly of contracted muscle. 
It occurs in the blood and at times in the urine, and it is prob- 
able that it is this modification that may be found as lactates 
and lactophosphates in the saliva and urine, the crystalline 
forms of which have been identified by Dr. E. C. Kirk of Phila- 
delphia, by the use of the micropolariscopic method of Dr. 
Joseph P. Michaels of Paris. This statement as yet lacks 
confirmatory demonstration. 

Both of these acids form characteristic crystalline salts of 
zinc and of calcium. In cold water the zinc sarcolactate is 
more soluble than zinc lactate; on the other hand, the cal- 
cium sarcolactate is rather less soluble than calcium lactate. 

^ oxybutyric acid, CHs-CHOH-CHsCOOH. If there is 
introduced into butyric acid, CH3-CH2-CH2-COOH, an OH 
group, an oxybutyric results. If this alcohol group (OH) 
occupies the secondary or /? position (i.e., attached to the car- 
bon atom twice removed from the carboxyl), the acid is the 
/? oxybutyric as above. 

By oxidation of the compound, the alcohol group is broken 
up and H withdrawn to form water, leaving a keto acid, 
CH3-CO-CH2-COOH, known as diacetic acid. This in turn 
may give off carbon dioxid and become dimethyl ketone, or 
acetone, CH3-CO-CH3. These three substances, ^ oxybutyric 
acid, diacetic acid, and acetone, are classed in von Noorden's 
Autointoxication, and by other recent writers, as '^ the acetone 
bodies," and by this convenient term we may refer to them 
collectively. They occur in diabetic urine and, according to 

* Dextrorotary. 



148 ORGANIC CHEMISTRY. 

von Noorden, in other cases of perverted oxidation (not insuffi- 
cient oxidation). 

Tartaric Acid is a dihydroxysuccinic acid, C00H-(CH0H)2- 
COOH, obtained from grape-juice. The double tartrate of 
sodium and potassium (Rochelle salts), KNaC4H406, is much 
used in medicine. 

Tartaric acid combines with potassium and antimony to 
form tartar emetic, (KSbOC4H406)2H20. 

The ''scale salts of iron,^^ ^' ferri et ammonii tartras" and 
^' ferri et potassii tartras," are prepared by dissolving freshly 
precipitated ferric hydroxid in the acid tartrate of ammonia 
or potash, and, after evaporation to thick syrup, solidifying in 
thin layers on glass plates. 

Potassium Bitartrate, or acid tartrate, KHC4H4O6, is cream 
of tartar, and one of the few salts of potassium, which are only 
sparingly soluble in water. Its commercial source is the wine- 
vat. 

Amido Acids, 
also called amino acids, are characterized by an NH2 group 

in place of H- ; for example, acetic acid is I . Amido- 

CH2NH2 
acetic acid is I . These acids are of particular interest 

because of their close relationship to the proteids, many of them 
being among the cleavage products of proteid hydrolysis. 

Amido-acetic Acid, also called glycocoll and glycin, is obtained 
with other amido acids by boiling glue with either acids or 
alkalis.* It is also obtained, by the hydrolysis of glycochoUc 
acid, from the bile. 

Hippuric acid (Plate V, Fig. 4) consists of benzoic acid 
united chemically to glycocoll, and may be produced synthetic- 
ally by the union of these two substances. 

* Bernthsen, Organic Chemistry. 



ORGANIC ACIDS. 149 

Amido-valerianic Acid, CH2(NH2)-(CH2)3-COOH, may be 
obtained with glycocoll from elastin, the proteid of the elastic 
fibres, of tendons, etc.* Isomeric with amido-caproic acid is 

leucin, an amido-isobutyl-acetic acid,t ptt^^H-CH2-CH(NH2)- 

COOH. Leucin is a cleavage product in the decomposition 
of proteids, including keratin and collagen. It results from 
the tryptic digestion of the hemipeptones and is regarded, as 
are other amido acids, as antecedent of urea (Plate V, Fig. 2). 

Dibasic Amido Acids. 

Of this class of compounds two may be mentioned: amido- 
succinic, aspartic or asparaginic acid, COOH-CH2-CH(NH2)- 
COOH, may be obtained from animal and vegetable proteids 
and in the pancreatic digestion of fibrin. 

Glutaminic Acid is an amido-glutaric (pyrotartaric) acid, 
and occurs similarly to aspartic acid, except that it is not formed 
by pancreatic digestion. 

Amins, or Substituted Ammonias. 

If one or more of the H atoms of ammonia, NH3, be replaced 
by a hydrocarbon group, the resulting compound is an amin; 
thus CH3-NH2 is methylamin, and (CH3)2NH is dimethylamin. 
Trimethylamin, (CH3)3N, has been found among the decom- 
position products of fresh brain, human liver, and spleen. J 
It is poisonous and possesses a strong, fishy odor. At ordi- 
nary temperature it is a gas, but, like ammonia, is freely soluble 
in H2O and forms a variety of salts. 

Diamins are derived from two molecules of ammonia, as 

ethylene diamin, C2H4^^u^ 

* Foster, Chemical Basis of vhe Animal Body. 

t Novy, Physiological Chemistry. 

I Vaughn and Novy, Cellular Toxins. 



15U ORGANIC CHEMISTRY. 

To this class of compounds belong many of the '^ ptomains," 
produced by the putrefaction of organic matter, as putrescin, 
butylene diamin, CH2NH2-(CH2)2-CH2NH2, and cadaverin, 
penta-methylene diamin, CH2NH2-(CH2)3-CH2NH2. A large 
number of the ptomaines are aromatic compounds and as 
such will be referred to later. 

Amids. 

If the hydrogen of NH3 be replaced by an oxygenated 
or acid radical, an amid results; thus NH2(C2H30) is acetic- 
amid, or this compound may be regarded as acetic acid, 
CH3-COOH, in which the OH has been replaced by NH2. This 
group (NH2) is known as the amido group, and characterizes 
a large number of very important compounds (see Amido Acids, 
page 148). 

Hydrazines. 

From diamid, NH2-NH2, or hydrazine, may be derived such 
substitution products as methyl-hydrazine, CH3-NH-NH2, 
ethyl-hydrazine, C2H5-NH-NH2, or phenyl-hydrazine, 
C6H5NH-NH2. 

This latter compound forms, with the monosaccharides and 
with many of the disaccharides, yellow crystalline compounds, 
known as osazones, w^hich are precipitated in characteristic 
crystalline forms, recognizable upon microscopical examination 
and by their melting-points (see under Carbohydrates). 

Experiments with Organic Acids. 

Experiments 18 and 19 may be used as illustrating the 
laboratory test for acetic and butyric acids. In addition a 
test for lactic acid may be made with ferric chlorid test, which 
is also applicable to gastric contents. 

Exp. 22. Dilute a few drops of neutral ferric chlorid solu- 
tion until no color is discernible, then to 10 c.c. of this dilution 



ORGANIC ACIDS. 151 

add 4 to 5 drops of 1/2% solution of lactic acid. A greenish- 
yellow color constitutes the test. 

In practical application of this test it needs further con- 
firmation by boihng the unknown solution with a drop or 
two of HCl and then extracting with ether. Evaporate the 
ether, take up the residue in 2 or 3 c.c. of water and repeat 
the test as given above. If the yellow color persists, it is due 
to lactic acid. 

Exp. 23. Introduce into a small flask (250 c.c. capacity) 
about 30 c.c. of anhydrous glycerine and an equal weight of 
oxalic acid crystals. Boil for several minutes; CO2 is given 
off and a compound formed between the acid and glycerine; 
then, upon addition of more acid and continued heating, formic 
acid may be distilled. Collect about 10 c.c. of distillate; test 
reaction with litmus-paper. Make silver-mirror test, described 
on page 142. The silver solution will be reduced, but difficulty 
will be experienced in obtaining the mirror. 

Exp. 24. From a mixture of formic acid, alcohol, and 
sulphuric acid, ethyl formate may be evolved in a manner 
similar to that in the production of ethyl acetate (page 49). 
Compare the odors of these two ethers. 

Exp. 25. To a dilute solution of permanganate of potas- 
sium add a few drops of sulphuric acid and heat nearly to 
boiling. Note if any change takes place. Now add a few 
crystals of oxalic acid and watch carefully. Explain the use 
of sulphuric acid. 

Exp. 26. In separate test-tubes, insoluble oxalates may 
be produced by adding a solution of ammonium oxalate to 
a solution of (a) calcium chlorid, (6) silver nitrate, (c) zinc 
sulphate, (d) copper sulphate, (e) lead nitrate. 

Exp. 27. To 1/3 test-tube of cider vinegar add a few 
cubic centimeters of basic acetate of lead solution; a bulky 
precipitate of lead malate separates out. 

Exp. 28. Take about 5 c.c. each of alcohohc solution of 
stearic and oleic acids and treat separately with about 2 c.c. 



152 ORGANIC CHEMISTRY. 

of 1% iodin solution (alcoholic); allow to stand for some time, 
and explain fully the difference in deportment exhibited by 
the two fatty acids. 

Exp. 29. To a dilute solution of ferric chlorid add a little 
acetic acid; divide the solution in two parts, and to one add 
mercuric chlorid and to the other HCl, and note results. 

SECTION v.— CYANOGEN COMPOUNDS. 

Cyanogen, C2N2, is an intensely poisonous gas, colorless, 
heavy (specific gravity 1.81), and inflammable. It is very 
easily soluble in water or alcohol, forming unstable solutions, 
which, upon decomposition, give rise to various nitrogen com- 
pounds, among them ammonia, hydrocyanic acid, and urea. 

Hydrocyanic Acid, HCN, may be produced by the fer- 
mentation of the glucoside amygdalin from bitter almonds; 
also from the kernel of peach-stones, cherry-laurel leaves, etc. 
HCN may be formed by direct synthesis of C2H2 (acetylene) 
and nitrogen. The synthesis is induced by passing electric 
sparks through the mixed gases. It is conveniently prepared 
in the laboratory by distilling a mixture of dilute sulphuric 
acid with potassium ferrocyanide, K4Fe(CN)6 + 5H2S04 = 
6HCN + FeS04 + 4KHS04. Hydrocyanic acid is a colorless, 
poisonous Hquid, boihng at 26.5° C, with a characteristic odor, 
often designated as a peach-stone odor. It is soluble in H2O, 
and a 2% aqueous solution constitutes the acidum hydro- 
cyanicum dilutum of the pharmacopoeia, also known as prussic 
acid. 

The organic cyanides are known as nitrils or isonitrils, 
according as the hydrocarbon radical is attached directly to 
the C or to the N or the cyanogen group. That is, methyl 
cyanid would be represented by CH3-CN, while the isocyanid 
would be CH3-NC (methyl carbamine); the nitrogen atom 
being in the first place trivalent, in the second quinquivalent. 

Of these two classes of compounds, the isocyanids are of 



CYANOGEN COMPOUNDS. 153 

much greater interest to tlie student of dental medicine owing 
to their relation to the isocyanates and to urea. 

Phenyl-isocyanid, C6H5NC, also known as isobenzonitril, 
is produced by warming aniline (C6H5NH2) with alcoholic 
potash and chloroform, the intensely disagreeable odor of 
which is utilized as a test for chloroform or chloral hydrate 
(page 142); or, with chloroform and potassium hydrate, the 
production of isocyanid may become a test for aniline, acetanilid 
(antifebrin), etc. 

Isocyanic Acid, = C = N-H (carbimid), is supposed to be 
the acid of ordinary potassium and ammonium cyanates. 

Fulminic acid (C^N-O-H), isomeric with cyanic acid 
N = C-O-H and isocyanic acid = C =- N-H, is important only 
because of its relation to the fulminates, which are explosive 
compounds of the acid, wdth some of the heavy metals, such 
as Ag and Hg. 

Thiocyanic Acid or Sulphocyanic Acid. — In this acid and 
its salts the atom of S replaces the oxygen of the cyanate in 
the empirical symbol (HCNS), but graphically the S is attached 
to the basic element (metal or H) rather than to C; thus, 
K-S-C = N, that is, the sulphocyanate is not an isocompound. 
For occurrence and relations of HCNS in the human body, see 
chapter on Saliva. 

Urea. 

This substance forms about 50% of the total solids and 
about 85% of the nitrogenous matter contained in the urine. 
When we consider that only 5% of the nitrogenous waste 
passes off in the feces and 95% in the urine, the importance 
of urea as an index of the nitrogen excreted, and of proteid 
metabolism, becomes apparent. 

Urea was the first organic substance synthesized from 
inorganic compounds. This was accomplished by producing 
a molecular rearrangement of ammonium isocyanate; the 
reaction is conveniently brought about by the double decom- 



154 ORGANIC CHEMISTRY, 

position of potassium cyanate and ammonium sulphate and 
subsequent evaporation of the solution to dryness : 

2CN0K + (NH4)2S0 = OCN.NH4 + K2SO4. 

Then = C = N-NH4 (ammonium isocyanate)+heat = 

/OTT 
Urea is the amid of carbonic acid, ^""^xOH' ^^^ ^^^^ ^^^^ 

type may be explained the rapid transformation of urea into 
ammonium carbonate in stale urine, ^^^xnh^ ^'^^^ ^^^ 

molecule of H2O becomes C) = C<^-^tt ^ or ammonium carba- 
mate, and this, by addition of a second molecule of water, be- 
comes 0"=C<^o"N'H* ^^ anmionium carbonate, (NH4)2C03. The 

last part of the reaction takes place whenever commercial 
'' ammonium carbonate " [really a mixture of carbamate 
(NH4-NH2-CO2) and acid carbonate (NH4HCO3)] is dissolved 
in water. 

Urea crystallizes in long needle-shaped crystals of the 
rhombic system. It is insoluble in water, somewhat soluble 
in alcohol, and nearly insoluble in ether. It fuses at 132^, and 
at a somewhat higher temperature it gives off ammonia and 
ammonium carbonate, and at 160° leaves a residue of ammelid, 
cyanuric acid, and biuret. Urea is decomposed by solutions 
of the alkaline hypochlorites or hypobromites being broken, 
up into N,C02, and H2O, as follows : 

C0(NH2) 2 + 3NaOBr = CO2 + N2 + 2H2O + SNaBr. 

Cyanuric Acid, (N3C3O3H3), is a polymer of cyanic acid, 
(NCOH), which is, at first, formed in the above decomposition. 



CYANOGEN COMPOUNDS. 155 

Biuret, H-N\^iq_xtj^J^, may be obtained by heating urea. 

When pure, it occurs as white, needle-shaped crystals. With 
NaOH and 1% CuSO it gives the characteristic violet and 
rose-red shades obtained in the biuret reaction (Piotrowski's 
proteid test). Exp. 74, page 185. 

Urea Nitrate may be precipitated from fairly concentrated 
urine by addition of HNO3. It separates in hexagonal crystals 
or plates, easily recognizable under the microscope (Plate V, 
Fig. 3). ^ 

Urea Oxalate. — Upon addition of a solution of oxahc acid 
to concentrated urine, crystals of oxalate of urea are precipi- 
tated. They are rather more easily obtained in character- 
istic forms (Plate III, Fig. 4) than are the crystals of nitrate, 
and, in consequence, treatment with oxalic acid constitutes 
a better method for the qualitative detection of urea in the 
body fluids than the nitric acid test formerly used. These 
crystals polarize light, and the use of the micropolariscope 
facilitates their detection. 

Substituted Ureas. — The hydrogen of the amido group 
may be replaced by alcohol radicals forming what are known 

as alkylated ureas; thus, ^ = C\MfTrH ^^ methyl urea, 

= C\^-vTTTri TT , ethyl urea, and one, two, three or all four 

of the H atoms may be so replaced. 

When, in place of an alcohol radical, the acid radical is 
introduced, a class of compounds known as ^' ureids " result; 

thus, = C<^^jj((.^jj^Q) (acetyl urea). 

,. COOH 
In case of a dibasic acid, such as oxalic, 1 , entermg 

COOH 

into the reaction, one or both (OH) groups may be split off, form- 

ing in the first instance a ureid acid, as = C<r Taxr^pQ COOH 
oxaluric acid, 



156 ORGANIC CHEMISTRY. 

COOH /NH2 /NH2 

I +0 = C< =0 = C< +H2O 

COOH ^NHs ^NH-CO 

I 
COOH 

/NH-C = 
or, in the second case, a ureid, as = C<^ | parabanic 

^NH-C = 

acid. 

If the residue of two molecules of urea enter into the com- 
position of the new molecule, the compound is a diureid. Of 
this class one of the most important is: 

Uric Acid, trioxypurin, C5n4N403. Its relation to urea 

NH-CO 

I I 
may be shown by the graphic formula = C C-NH\ 

I II > = 
NH-C-NH^ 

Uric acid is also referable to a purely hypothetical base, ^' purin," 

by the use of which the relationship of xanthin, hypoxanthin, 

and other ^' purin " or nuclein bases is easily demonstrated. 

These bases are of great physiological interest, in that they 
form an unquestioned link between the decomposition products 
of the proteids, nuclein, etc., on the one hand, and uric acid 
and the urates on the other. 

Purin is represented by the formula C5H4N4, or graphically 
N = C-H 

as H-C C-N-H . If we now break all double bonds except 
€-H 



N— C-N^ 

those linking two carbon atoms (4 and 5), we obtain a graphic 

1— N-C6 

I I 
nucleus, 2 = C C'^-N^T , by numbering the atoms of which 

I II > = 8 
3— N-C*-N/9 



CYANOGEN COMPOUNDS. 157 

we may easily designate any structural formula of the group ; thus, 
2-6-8, trioxypurin, is uric acid as above, while xanthin is 2-6, 
H-N-C = 



dioxypurin, = C C-N-H , and 1-3-7, trimethyl-xanthin, 

I II 

H-N-C-N' 



V..H 



CH3-N-C = 

I I 
= C C— N^CHs, is caffein and thein, alkaloids from coffee 

I il >C-H 

and tea. 

Traces of xanthin (2.6 dioxypurin), hypoxanthin (6 oxy- 
purin), guanin (2 imido, 6 oxypurin), adenin (6 amido purin), 
and heteroxanthin (7 methyl xanthin) have been found in 
urine, and, in cases of leukaemia, many of them in increased 
amounts, notably xanthin, hypoxanthin, and adenin (Witt- 
haus) . 

Uric acid occurs in the urine, traces in the blood and occa- 
sionally in saliva as urates. It is a dibasic crystalline acid, 
colorless when pure; but in urinary sediment it occurs gener- 
ally as crystals yellow to red, " whetstone "-shaped, and in 
various other forms (Plate V, Figs. 5 and 6). The " brick- 
dust " deposit occasionalh^ found in urine consists of uric acid. 
It is insoluble in alcohol and nearly insoluble in water; but 
its solubility in water is increased by the presence of urea. 

Upon heating uric acid, urea and cyanuric acid may be 
obtained; NH3 and CO2 are given off. We are not to infer 
from this decomposition that the uric acid is an antecedent 
of urea in the animal body; for such is not the case, except 
possibly to a limited extent. 

Uric acid produces, upon oxidation, a variety of com- 
pounds, according to the temperature and the oxidizing agent 
employed. 

CI hot yields cyanuric acid, C3H3(OH)3. CI or Br cold 



158 ORGANIC CHEMISTRY. 

forms oxalic acid, alloxan, (^C)\mhCO/^^^' parabanic acid, 

/NH-COl 
(C0<^ I \ and ammonium cyanate. HNO3 in the cold 

\nH-COj 
forms alloxan, alloxan tin, and urea (Witthaus). 

Uric acid may be detected by the murexid test. See 
Exp. 39, page 160. 

Note. — Murexid is a definite chemical compound (CgHgNjOg) and may be 
produced from alloxantin, an oxidation product noted above. 

While uric acid is practically insoluble in H2O and the acid 
urates only sparingly soluble, the uric acid in the system is 
apparently held in solution as an acid urate (NaHU) by the 
presence of the sodium phosphates, NaH2P04 and Na2HP04, 
possibly also aided by the presence of some unknown organic 
combination. 

NaHU + NaPl2P04 forms at 38° C. a solution with an acid 
reaction, if, however, the mixture is cooled to room tempera- 
ture, the reaction becomes alkaline from Na2HP04 and uric 
acid is precipitated (Bunge) : 

NaHU + NaH2P04 = Na2HP04 + H2U. 

Na2HP04 is a normal constituent of the blood, and a tendency 
to precipitate uric acid may be met by the following reaction: 
Na2pIP04 + H2U = NaH2P04 + NaHU. Because the acid urate 
of lithium is much more soluble in water than any of the other 
monometallic urates, lithium salts have long been used as 
uric acid solvents. But the fact that lithium solutions will 
precipitate from solutions of Na2HP04 crystals of Li2HP04 
has been made the basis for a claim that such use of lithium 
salts is without effect other than to decompose and render 
insoluble the alkaline phosphate, which has been acknowledged 
a valuable factor in keeping uric acid in solution. While the 
disodic phosphate is regarded by many as superior to lithium 
salts as a uric acid solvent, the fact of comparative insolu- 



CYANOGEN COMPOUNDS. 159 

bility of Li2HP04 can hardly be regarded as conclusive evidence 
that lithium compounds are rot effective. 

The following in regard to our need for ''sarsaparilla" in 
the spring is given by Dr. E. C. Hill, of the University of Denver, 
in his text-book of chen\istry, p. 370: "Reduced alkalinity of 
the blood, as in winter from eating meats freely, throws uric 
acid out of solution to collect in the more acid tissues (spleen, 
liver, and joints). With the vernal tide of alkalinity (due to 
freer sweating, with excretion of fatty acids) these deposits 
are swept out in the blood-current, irritating the nerves and 
giving rise to 'that tired feeling.' " 

Experiments with Cyanogen Compounds and Urea. 

Exp. 30. In a test-tube dissolve i gram or less of potassium 
ferrocyanid in about 4 c.c. of H2O. Add a little H2SO4 and 
boil, conducting the gas evolved into another test-tube by 
means of a bent glass tube. Note the odor of this dilute solu- 
tion. (Do not smell of the contents of generating-tube, as the 
strong acid is intensely poisonous.) 

2K4FeCy6 + 6H2SO4 = K2Fe(FeCy6) 4- 6KHSO4 + 6HCy. 

Exp. 31. To one half of the dilute hydrocyanic acid prepared 
in the previous experiment add a drop or two of AgNOs solu- 
tion with a Httle HNO3. After the precipitate has settled, 
decant the fluid, then add an excess of ammonia-water. 

Exp. 32. To the other half of the HCy from Exp. 30 add a 
little solution of ferrous sulphate; also a few drops of ferric 
chlorid solution; then a little KOH solution; mix thoroughly 
and acidify with HCl, a blue precipitate, in Fe4(FeCy6)3. 
This constitutes a test for HCy or any soluble cyanid. 

Exp. 33. To a few drops of KCN solution add a little yellow 
ammonium sulphid, (NH4)2S, and evaporate to dryness. Dis- 
solve in water; acidify with HCl and add Fe2Cl6 solution. 

Exp. 34. Make separate solutions of 10 grams of potassium 



160 ORGANIC CHEMISTRY, 

cyanate * and 8.25 grams of ammonium sulphate. Mix and 
evaporate on a water- bath in a shallow dish. Separate the 
potassium sulphate as the evaporation proceeds; finally^ 
evaporate to dryness and extract with absolute alcohol. Evap- 
orate alcohol and reserve the urea for subsequent experiments.. 
(See Urea, page 154.) 

Exp. 35. Heat a few crystals of urea in a test-tube till it- 
fuses and no more gas is given off; cool, and dissolve the fused 
mass in water; add one or two c.c. of strong NaOH solution,, 
then not more than one or two drops of a 1% CUSO4 solution- 
Note the pink to violet color produced. This constitutes the 
biuret reaction used in physiological chemistry as a test for 
albumoses and peptones. Biuret is formed from urea as follows : 

^NH2 
2 = C^S£ = S:^>NH + NH3. 

\NH2 

Exp. 36. Produce crystals of urea nitrate and oxalate 
(page 155) and examine under the microscope. Repeat with 
urea obtained from urine. 

Exp. 37. Treat 5 c.c. of urea solution (urine may be used) 
with a little sodium hypochlorite or hypobromite; note results 
and study reaction given on page 154. 

Exp. 38. Heat a third of a test-tube of urine with barium 
hydroxid (baryta-water); test vapor with red litmus for NH3.. 

Exp. 39. Murexid test for uric acid : Place a very small quan- 
tity of uric acid on a porcelain crucible cover, or in a small 
evaporating-dish. Add two or three drops of strong nitric acid 
and evaporate to dryness over a water-bath. A yellowish-red 
residue remains, which changes to a purphsh red upon addition 
of a drop of strong NH4OH, and purple-violet upon further 
addition of a drop of KOH solution, the color disappearing 

* For method of making potassium cyanate, see Preparation of Reagents, 
and Organic Compounds, in the Appendix. 



CLOSED-CHAIN HYDROCARBONS. 161 

upon standing or upon the application of heat. (Difference 
from xanthin, which also gives a much redder color.) 

Exp. 40. Repeat No. 37, using caffein in place of uric acid. 

Exp. 41. Heat a little sodium acid urate in a dilute solution 
of NaH2P04. Allow to cool, and examine any deposit for uric 
acid crystals. Test reaction of solution both hot and cold 
(page 158). 



SECTION VI.— CLOSED-CHAIN HYDROCARBONS. 

In illustrating the simpler relationship of organic compounds 
we have, as far as possible, carefully avoided reference to the 
closed-chain or aromatic compounds, as the characteristic 
groupings are more easily seen by the use of simple formulae. 
The distinguishing feature of the aromatic (also called cyclic) 
compounds is a nucleus consisting of a closed chain of atoms; 
this chain may contain three, four, five, six, or seven members, 
but the six-carbon ring is by far the most important, and the 
only one which we are to consider. 

The hydrocarbons of the aromatic series have, for a general 
formula, CnHsn-gj the simplest being benzene or benzol, 
CeHg; and from this we may consider that the aromatic com- 
pounds are derived. The structure of the benzene molecule 
is represented by ''Kekule's" benzene ring. H 

Note that there are three double bonds, which | 

of course permit of addition products, as //\ 

C6H6CI2, benzene di-chlorid, etc. The substi- H-C C-H 
tution products are, however, of far greater I |! 

importance. X / 

The next higher homologue of the series will ^C^ 

be CyHs; this is methyl benzene, (C6H5CH3), | 

or toluene. The dimethyl benzenes are the ■"■ 

xylenes, three in number, C6H4(CH3)2, or CgHio. Note the 
possibility here existing for isomeric compounds, as follows: 



162 ORGANIC CHEMISTRY. 



CH3 CH3 CH, 

\CH3 



r 



ICH. ^^^ 



CH. 



These three possible positions of the second substitution are 
known as ortho-, meta-, and para-; thus, in the more famiUar di- 
hydroxybenzene we have 

C>H , ,., , OH 

or^/io-dihydroxy /^ meta-dihydroxy 



QJJ benzene or / \ benzene or 

pyrocatechin j \r\jT 



and 

OH 



para-dihydroxy 

benzene or 
hydroquinone 



OH 



Of these three dihydroxybenzenes, the ortho compound, 
pyrocatechin, is of particular interest. Its ethereal sulphate 
(acid sulphate) is given by Hoppe-Seyler as a constituent 
of normal urine, and its monomethyl ether guaiacol, 
CeHiOH-O-CHs, is obtained from beech-wood creosote, of 
which it constitutes a greater part (60 to 90 per cent U. S. D.). 
Guaiacol and various compounds produced from it have been 
widely recommended for tubercular diseases. 

A trisubstituted benzene may be ^'adjacent," if the sub- 
stituted element or group is attached to carbon atoms, 1-2-3, 
or ''unsymmetrical" (1-2-4) or ^'symmetrical" (1-3-5). 

Benzene, CqRq, is a colorless liquid from the ''light-oil" 
obtained by distillation of coal-tar. It boils at 80°, has a 
gravity of 0.899, soluble in ether, alcohol, and chloroform, 
but insoluble in H2O. It may be made pure by distilling an 
intimate mixture of benzoic acid and quicklime, and at a tem- 



1 



CLOSED-CHAIN HYDROCARBONS. 1G3 

perature of about 5° C. may be obtained as a crystalline solid, 
CeHsCOOH+CaO^CaCOs + CeliG. (See Exp. 40.) 

Nitro-benzene, C6H5NO2, may be produced by treating l)eri- 
zene with a mixture of nitric and sulphuric acid at reduced 
temperature. (Exp. 42, page 167.) It is a yellow oily liquid 
with the odor of bitter almonds, commercially known as oil of 
mirbane, and used in the manufacture of aniline. 

Amido-benzene, C6H5NH2. By reaction of nitrobenzene with 
nascent hydrogen, the NO2 group becomes an NH2 group and 
amidobenzene or aniline is produced. Aniline is a colorless 
liquid, also called aniline oil, and is the basis of a large number 
of complex compounds, the aniline dyes. 

Methyl-benzene or Toluene, CeHsCHs, is a colorless liquid 
obtained from coal-tar and a valuable reagent in organic chem- 
istry. It may be oxidized to benzoic acid, CeHsCOOH. 

Dimethyl-benzene or xylene, C6H4(CH3)2, is a valuable 
solvent nmch used in chemical and bacteriological labora- 
tories. There are three isomeric forms, the ortho-, meta-, and 
para-. 

Phenol, carbolic acid, is oxybenzene, CeHsOH, obtained 
from the distillation of coal-tar, and used as an antiseptic and 
disinfectant. For properties and test, see page 111. Phenol 
acts like an acid, in that it forms salts with the metaUic bases, 
CeHsOK, potassium phenolate. 

Phenol Sulphonic Acid. — When phenol is treated with several 
times its volume of cold, strong H2SO4, phenol sulphonic acid 
OH OH 



results, { I HSO3 or f ^ . If the mixture is heated for some 



HSO3 

time over a water-bath, the disulphonic acid results. This acid, 
warmed with a nitrate and the mixture treated with excess 
of ammonia, yields ammonium picrate, and constitutes a deli- 
cate test for nitrates present in drinking-water. (See Exp. 49, 
page 168.) 



164 ORGANIC CHEMISTRY. 

Phenyl Sulphuric Acid, C6H5HSO4, occurs only in combina- 
tion, the acid being unstable if attempt is made to isolate it. 
Its potassium salt is present in the urine as a product of in- 
testinal putrefaction. 

Picric Acid is trinitrophenol, C6H2.0H.(N02)3. It may be 
formed by action of strong HNO3, or mixture of H2SO4 and 
HNO3 on phenol. It occurs as yellow plates shghtly soluble 
in H2O, easily soluble in alcohol and ether, and is used in 
Esbach's reagent for the estimation of albumin in urine and 
as an alkaloidal precipitant. 

Phloroglucin, used in physiologial chemistry as a reagent 
with vanillin, is a trihydroxybenzene, Cells (OH) 3(1,3 5). It crys- 
tallizes in rhombic prisms, soluble in water, alcohol, and ether. 

Benzoic Acid, CeHsCOOH, originally produced from gum 
benzoin, but may be made from hippuric acid (q. v.), and this 
(from urine of horses) formerly constituted a commercial 
source. It is chiefly prepared, however, from toluene; it 
crystallizes in colorless plates or long prismatic crystals (from 
solution) . Sparingly soluble in cold water, more soluble in hot 
water, and easily in alcohol. It sublimes and is inflammable, 
burning without residue. 

Benzoates of sodium, ammonium, lithium, and of lime are 
all used in medicine. Benzoated lard is prepared by digesting 
gum benzoin in hot lard. This is much used as a base for 
ointments and keeps well. 

Benzaldehyd, CeHs-CHO, is a colorless liquid, soluble in 
alcohol and ether, and sparingly in water. The U. S. P. oil 
of bitter almonds is practically benzaldehyd; it is a volatile 
oil, very poisonous, and upon standing deposits benzoic acid 
from partial oxidation. 

SalicyUc Acid, orthohydroxybenzoic acid, C6H4-OH.COOH, 
a white crystalline powder, odorless, irritating to mucus sur- 
faces, soluble in alcohol and ether, and in about 450 parts of 
water at 15° C. (U. S. D.). Salicjdic acid may be made by 
action of CO2 on sodium phenate and subsequent decompo- 



CLOSED-CHAIN HYDROCARBONS. 165 

sition of the sodium salicylate. By heating rapidly the acid 
may be changed into carbolic acid and CO2. 

Salicylates have been used to considerable extent in various 
uric-acid diseases. Methyl salicylate constitutes 90% of natu- 
ral oil of wintergreen (page 138). The alcoholic solution is 
essence of checkerberry. 

Salol is phenylsaUcylate, C6H40H.COO(C6H5), a white 
crystalline powder, practically insoluble in water and not de- 
composed by the dilute acids of the stomach juices; but in the 
intestine it becomes salicylic acid and phenol, as follows: 

C6H4.OH.COOC6H5 + H2O = C6H4OH.COOH + CeHsOH. 

Anilin, amidobenzene, C6H5NH2, may be made by reduction 
of nitrobenzene by nascent hydrogen. This substance is im- 
portant from a commercial rather than from a medical 
standpoint, as it forms the basis of the anilin dyes. When 
pure it is a colorless liquid, but changes quite rapidly when 
exposed to the light. Used in testing for chloral and chloro- 
form. Slightly soluble in water, and easily soluble in alcohol 
and ether. At 8° C. it becomes a crystalline solid. 

Hippuric Acid, benzoyl glycocoll, C6H5.CO.NH.CH2-COOH, 
occurs in traces in human urine, to a considerable extent in 
the urine of the herbivora, and not at all in that of the car- 
nivora. It crystallizes in prismatic needles (Plate V, Fig. 4), 
often resembhng crystals of ammonium magnesium phosphate; 
but as these latter only occur in neutral or alkaline urine and 
hippuric acid, usually in acid-urine, there is little danger of 
confounding the two substances. Hippuric acid is hydrolysed 
by the urease of fermenting urine, forming benzoic acid and 
glycocoll (amido-acetic acid) : 

C6H5.CO-NH-CH2-COOH -h H2C 

= C6H5COOH -fCH2NH2COOH. 

Tryosin, C6H4.0H.-CH2CH(NH2)-COOH, may be crystal- 
lized as fine silky needles. It is formed from proteid sub- 



166 ORGANIC CHEMISTRY. 

stance, particularly casein and fibrin, both by the action of 
proteolytic enzymes and by putrefactive processes. It rarely 
occurs in urinary sediment in bundles or sheaves (Plate VI, 
Fig. 1), and when found it is usually indicative of acute liver 
disease, phosphorus poisoning, etc. 

Heterocyclic Compounds. — ^The closed-chain or cyclic com- 
pounds are known as isocyclic or homocyclic when the atoms 
constituting the ''ring" or nucleus of the molecule are all of 
the same sort (carbocyclic, if all of carbon), as has been the 
case in all the aromatic compounds which we have thus far 
taken up, i.e., the structure of compounds has been based 
upon the six-carbon or benzene ring. If the ring is made up 
of atoms of different sorts the compound is heterocyclic, and 
one or two of these are of importance. 

First, pyridin, C5H5N, which may be regarded as benzene in 
which one CH group has been replaced by an atom of nitrogen : 

H 

/\ 
HC CH 

I II 

HC CH 

It is a liquid miscible with water, boiling-point 115° C. 
Second, quinalin, C9H7N, a colorless liquid. 

H H 

HC C CH 

I I II 

HC C CH 

\c/\n/ 

H 

And upon one or the other of these two bases may be 
constructed the graphic formula of many of the vegetable 
alkaloids. 



CLOSED-CHAIN HYDROCARBONS. 167 

A certain number of alkaloids, such as caffein, thein (tri- 
niethylxanthin), are referable to the purin nucleus (page 156). 

PI 

HC C CH 

Indol, CsHyN,— | || || ,— is produced from pro- 

HC C CH 

\c/\n/ 

H H 

teid by the putrefaction occurring in the small intestine; also by 
action of the proteolytic enzyme of the pancreatic juice (trypsin). 
The indol, by oxidation (after absorption from the intestines), 
becomes indoxyl, CgHeNO, which, with K2SO4, forms indoxyl- 
potassium sulphate, C8H6NKSO4, and as such is eUminated 
(in part) by the kidneys. This substance is a type of the so- 
called ethereal or conjugate sulphates, skatoxyl-potassium sul- 
phate (skatol) and phenol-potassium sulphate being other com- 
pounds of this class. The ethereal sulphates are not precipi- 
tated by BaCU in alkaline solutions, but may be decomposed 
by prolonged boiling with HCl and then precipitated as usual. 

The oxidation of indoxyl produces indigo blue, and this fact 
is utilized in the quaUtative test for indoxyl in urine (q. v.) . 

/C.CHs^ 

Skatol, methylindol, C6H4\ yCH, occurs in similar 

NNHX 
manner to indoxyl, and likewise passes into the urine as an 
ethereal sulphate (skatoxyl-potassium sulphate). Skatol is a 
constituent of the faeces and possesses a strong faecal odor. 

Experiments with Aromatic Hydrocarbons. 

Exp. 42. Into a small and thoroughly dry flask (250 c.c.) 
introduce about 50 grams of a mixture consisting of one part 
of benzoic acid and two parts of quicklime; connect with a 
condenser and heat. Benzole (benzene) distils over: 

CaO + CeHsCOOH = CaCOa + CeHg. 



168 ORGANIC CHEMISTRY. 

Exp. 43. Turn a little of the benzene prepared in the last 
experiment on to some water contained in a porcelain capsule. 
Set fire to it and note that it burns with a smoky flame. Cool 
a little pure benzene by immersing a few cubic centimeters, con- 
tained in a narrow test-tube, in a freezing mixture of ice and 
salt. 

Exp. 44. In a wide test-tube mix 5 c.c. of concentrated 
H2SO4 with about half its volume of strong HNO3; cool in ice- 
water or cold running water, and add very slowly about 2 c.c. 
of benzene. Nitrobenzene is formed and may be separated as 
a heavy oily liquid by pouring the mixture into an excess of 
water. Notice the odor of oil of bitter almonds. 

Exp. 45. To a few cubic centimeters of a 3% carbolic acid 
solution add dilute bromin water. A yellowish-white crystal- 
line precipitate of tribromphenol is produced. (See page 111.) 

Exp. 46. To an aqueous solution of carboHc acid add a 
few drops of solution of ferric chlorid. 

Exp. 47. Boil 15 c.c. oil of wintergreen with 20% NaOH; 
keep the volume constant by frequent addition of water. When 
the oil has entirely disappeared, cool and add HCl to acid reac- 
tion. SaUcylic acid will separate, white and crystaUine. 

Exp. 48. To a dilute solution of sodium salicylate, or satu- 
rated aqueous solution of salicylic acid, add a few drops of 
Fe2Cl6. Slight amount of salicylates in the urine will produce 
this color when test is being made for diacetic acid (q. v.). 

Exp. 49. Evaporate a few drops of a 1% solution of potas- 
sium nitrate to dryness in a small porcelain capsule. Add 
2 c.c. of phenoldisulphonic acid;* stir thoroughly, and keep 
hot for three to five minutes; dilute with water and make 
strongly alkahne with ammonia, and note the intense yellow 
color of ammonium picrate. The reaction is used as a test 
for nitrates in drinking-water. 

* For method of preparation of phenoldisulphonic acid, see Appendix. 



PART VI. 

PHYSIOLOGICAL CHEMISTRY, 



SECTION I.— FERMENTS. 

The study of Physiological Chemistry includes the sub- 
stances which go to make up the animal body, the changes 
which these substances undergo in the process of digestion and 
assimilation, and the final products of metabolism. 

This subject, like others, will receive our attention in out- 
line, with a view simply to enable the student to understand 
the conditions which at present seem to have the most direct 
bearing on dental science. The changes produced by the 
class of bodies known as ferments are of great importance and 
the first to be considered. 

If yeast is allowed to grow in a sugar solution of moderate 
strength, the sugar molecule is split into carbonic-acid gas and 
alcohol. The process is one of fermentation, the yeast is the 
ferment. There are various substances which cause similar 
splitting of complex molecules into simpler compounds,* and 
the)^ may be classified as organized and unorganized ferments. 

The organized ferments are possessed of a definite organism 
and are represented by the yeast-plant, the lactic acid bacillus, 
and many other micro-organisms capable of bringing about 
these changes. The unorganized ferments are known as 
Enzymes, and are of the nature of protein substances lacking 
a specific organization. They exist within the cell, oftentimes 
as a zymogen or parent-enzyme, from which the enzyme itself 

* Occasionally fermentation may produce a synthesis (putting together) 
rather than an analysis (pulling apart). 

169 



170 



PHYSIOLOGICAL CHEMISTRY. 



is produced, as illustrated by the pepsinogen (zymogen) exist- 
ing in the stomach-wall, which, by action of HCl of the gastric 
juice, becomes the pepsin (enzyme) in the stomach (q. v.). 

'^ Hydrolysis " is a term used to describe the breaking-up of 
complex molecules and the utilization of a molecule of water 
in the production of the new compounds. By hydrolysis, or 
hydrolytic cleavage, the molecule of cane-sugar, C12H22O11, be- 
comes two molecules of a simpler sugar, such as glucose, C6Hi206» 
C12H22O11 +H20 = 2C6Hi206. Many enzymes produce molec- 
ular changes in this way, and in consequence are called hydro- 
lytic enzymes. The name of the substance acted upon may 
also be used to designate an enzyme ; thus a proteolytic enzyme 
produces a cleavage of proteid substances. A lipolytic enzyme 
(lipase) splits the fat molecule, etc. 

The name of a specific enzyme usually ends in ^'ase," as 
hpase (as above); zymase, the enzyme contained in yeast; 
urease, the urine ferment, etc. Their action is effected in 
marked degree by the character of the media in which they 
work, and by the temperature employed. Hydrolysis may 
also be brought about by chemical action, as illustrated by "the 
conversion of starch into glucose by boiling with very dilute 
mineral acid, HCl or H2SO4. 



SECTION II.— CARBOHYDRATES. 



Classification 



Sugars - 



Dextrose 
Lsevulose 
Galactose 



Monosaccharids, 



Starch 



Saccharose 1 

Maltose |- Disaccharids. 
i Lactose 

f Starch 



1 Glycogen 



Gum { Dextrin 
Cellulose 



Polysaccharids 



CAR BOH YDRA TES. Ill 

Characteristics. — The inonosaccharids are reducing bodies of 
either the aldehyde or the ketone type. The termination "ose " 
is applied to all sugars, and may also be used in designating 
the type; thus dextrose is an ''aldose," while hrvulose is a. 
"ketose." The monosaccharids above mentioned have the 
formula C6H12O6. They all reduce Fehling's copper solution 
(galactose less easily than the others), and they are all fer- 
mented by yeast (galactose more slowly than the others). 

Disaccharids have the general formula C12H22O11. They 
are converted into the monosacchardis by hydrolysis brought 
about either by action of enzymes or by boiling with mineral 
acid. 

The polysaccharids of the above group have the general 
formula (CgHioOo).!*. They lack the sweet taste which the 
sugars possess in varying degrees. They may all be converted 
by action of acids into monosaccharids, although the change 
is effected in cellulose with some difficulty. 

Dextrose or Glucose, C6H12O6, also known as grape-sugar 
and as diabetic sugar, occurs in grapes, honey, etc. It is 
formed by the action of diastatic ferments on the disaccharids; 
also from many of the polysaccharids. Glucose thus occurs in 
the processes of digestion and constitutes the sugar of diabetic 
urine. It may be obtained commercially as a white solid, and 
also as a thick, heavy syrup known as confectioners' glucose. 
The commercial glucose is prepared by the action of dilute 
acids on starch when hydrolysis takes place, as follows: 
CeHioCs -f H2O = C6Hi206. Glucose contains an aldehyde group, 
-COH, in consequence of which it is sometimes termed an 

aldose, in distinction from the ketones, which contain the C^O 

I 
group, of which hievulose is an example. 

Tes^s.— Glucose boiled with Fehling's solution precipitates 
the red suboxid of copper (CU2O). 

Glucose responds to Molisch's test for carbohydrates, which 
is made with an alcohoUc solution of a-naphthol and concen- 



172 PHYSIOLOGICAL CHEMISTRY. 

trated sulphuric acid. (Exp. 51.) It may be distinguished 
not only from other carbohydrates but from other sugars by 
heating with Barfoed's solution (copper acetate in dilute acetic 
acid), which is reduced with precipitation of CU2O. 

Heated with phenylhydrazine solution nearly to the boiling- 
point of water, glucose forms phenylglucosazon, which crystal- 
lizes, as the mixture cools, in characteristic yellow needles, 
usually arranged in bundles or sheaves. (Plate VI, Fig. 2.) 

Osazones are the various compounds formed by the different 
sugars and phenylhydrazine when treated as above. They 
crystallize in fairly distinctive forms and furnish valuable tests 
for the sugars, this method being considered at least ten 
times more deUcate than Fehling's test. Glucose readily under- 
goes alcoholic fermentation, yielding C2H5OH and CO2. (See 
Exp. 58.) 

Laevulose, C6H12O6, or fruit-sugar, turns the ray of polarized 
light to the left, and to a greater degree than glucose turns it to 
the right. It occurs in honey and in many fruits, and is pro 
duced with glucose by hydrolysis of cane-sugar. Lsevulose 
forms an osazone not to be distinguished from glucosazone. It 
reduces copper solutions in a manner similar to glucose, and, 
Hke it, is easily fermented by yeast. 

Galactose is the product of the hydrolysis of lactose, or milk- 
sugar, and some other carbohydrates. It is a crystalline sub- 
stance which reduces Fehling's solution and ferments slowly 
with yeast. 

Cane-sugar, C12H22O11, sucrose or saccharose, obtained from 
the sugar-cane (various varieties of sorghum), also from the 
sugar-beet {Beta vulgaris) and the sugar-maple (Acer saccha- 
rinum). Cane-sugar is a white crystalHne soHd soluble in about 
J part of water and in 175 parts of alcohol (U. S. P.). It does 
not reduce copper solutions, nor does it form an osazone with 
phenylhydrazin; but it is easily hydrolyzed with the formation 
of dextrose and hevulose, and then, of course, the reactions 
peculiar to these substances may be obtained. It does not 



CARBOIIYDRA TES. 173 

ferment directly, but, by the action of invertin contained in 
yeast, it takes up water, becoming glucose and lavulose as 
above, these latter sugars being easily fermentable. 

Maltose, C12H22O11, or malt-sugar, is an intermediate prod- 
uct in the hydrolysis of starch, and by further hydration be- 
comes two molecules of dextrose : C12H22O1 1 +H2O ^ 2C6H12O6. 
It is formed in the fermentation of barley by diastase (the 
ferment of malt), and with phenylhydrazine it produces an 
osazone distinguished from glucosazone and lactosazone by its 
microscopical appearance (Plate VI, Fig. 3) and its melting- 
point. 

Lactose, C12H22O11, obtained from milk, is a disaccharid 
with far less sweetening power than sucrose. It forms an 
osazone which crystallizes in small burr-shaped forms (Plate VI, 
Fig. 4). It reduces Fehling's solution, but does not reduce 
Barfoed's solution. It resists fermentation in a marked de- 
gree. Upon hydration it is converted into dextrose and galac- 
tose. 

Starch. — This well-known and widely distributed plant- 
constituent is a carbohydrate represented by CeHioOs, the 
actual molecule, however, being many times this simple for- 
mula. The microscopical appearance of the starch granule is 
quite characteristic, and recognition of the more common 
starches by this method is not at all difficult. (See Plate Yll.) 

Starch is not soluble in cold water, but in hot water, or in 
solutions containing ^'amylolytic " enzymes, or in solutions 
containing certain chemical substances, as chlorid of zinc or 
of magnesium, dilute HCl or H2SO4, capable of forming hydro- 
lytic products, the starch granules swell up, and ultimately 
dissolve, being converted into dextrose. The conversion, how- 
ever, takes place in several well-defined steps, as follows : Solu- 
ble starch is first formed, answering the same chemical test with 
iodin (Exp. 169, c) ; next erythrodextrin, which gives a red 
color with iodin solution; then achroo- and maltodextrin, which 
give no color with iodin, but react sHghtly with Fehling's copper 



174 PHYSIOLOGICAL CHEMISTRY. 

solution; then maltose, also negative with iodin, but reacting 
strongly with Fehling's solution; and finally dextrose. 

Dextrin (CeHioOs) is a yellowish powder, also known as 
British gum; is formed from starch, as indicated above; con- 
stitutes to a considerable extent the ^' crust" of bread; is solu- 
ble in water, the solution giving a red color with iodin; and is 
further distinguished from starch by its failure to give a pre- 
cipitate with solution of tannic acid. 

Glycogen, or animal starch, is a carbohydrate, with the gen- 
eral formula CeHioOs, occurring principally in the liver, and to 
a lesser extent in nearly all parts of the animal body. Freshly 
opened oyster is a convenient source of the substance for labo- 
ratory demonstration. It occurs in horse-flesh in considerably 
larger proportions than in human flesh. 

Properties. — Glycogen is a white powder without odor or 
taste. It dissolves in water, producing an opalescent solution. 
It is closely allied to the starches of vegetable origin in that 
the products of its hydrolysis are dextrin * and ultimately 
dextrose. It differs in its ready solubihty in water, and in the 
fact that it is precipitated by 66% alcohol; also in its power of 
rotation, which is much stronger than that of starch. 

Physiology. — Glycogen is formed by the liver, and stored by 
this same organ for future use. It is derived principally from 
carbohydrates, but may also be derived from proteids. It dis- 
appears during starvation. In dead Hver or muscle it rapidly 
undergoes hydrolytic change with the production of a reducing 
sugar. 

Cellulose, CeHioOs, is a carbohydrate which occurs as a 
principal constituent of woody fibre, and which may be found 
in the laboratory in nearly a pure state, as absorbent cotton 
or Swedish filter-paper. It is insoluble in water, alcohol, or 
dilute acids; it may be dissolved, however, by an ammoniacal 
copper solution. It is converted into rnonosaccharids by acids 

* Foster's Text-book of Physiology. 



CARBOHYDRATES. 175 

only after first treating with concentrated H2SO4, which i)ar- 
tially dissolves it. Cellulose aids digestion in a purely mechan- 
ical way; treated with a mixture of nitric and sulphuric acids, 
it is converted into nitro-substitution products which are known 
as guncotton. The soluble cotton from which collodion is pre- 
pared is a mixture of tetra- and pentanitrates, while the more 
explosive but insoluble guncotton is a hexanitrate, formerly 
known as trinitroccllulose. 

Experiments with Carbohydrates. 

Monosaccharids. — Exp. 50. Test for C and H, using cane- 
sugar. Make closed- tube test for H, which is given off as H2O, 
and for C, which remains as such in tube. (See page 123.) 
Write reactions. 

Exp. 51. Molisch's Test for Carbohydrates. — To a few cubic 
centimeters of a 3% glucose solution add a few drops of an 
alcohohc solution of a-naphthol, and carefully underlay the 
mixture with strong H2SO4. 

Exp. 52. To a few cubic centimeters of CUSO4 solution in a 
test-tube add a Uttle NaOH. Boil and write reaction. 

Exp. 53. Repeat Exp. 52 with the addition of Rochelle salt; 
if solution remains clear on boiling, add a few drops of a glucose 
solution. 

Exp. 54. Fehling's Test for Sugars. — Take about 5 c.c. of 
Fehling's solution * made by mixing equal parts of the CUSO4 
solution and the alkaline tartrate on side shelf. Boil and add 
immediately a few drops of glucose solution. Set aside for a 
few minutes, watching the results. 

Exp. 55. Repeat Exp. 54, using diabetic urine. 

Exp. 56. Repeat Exp. 54 without heat and allow to stand 
twenty-four hours. 

Exp. 57. Barfoed's Test. — To about 5 c.c. of Barfoed's 
reagent add a few drops of glucose solution; boil, and set aside 
for a few minutes, watching results. 

* For preparation, see Appendix. 



176 



PHYSIOLOGICAL CHEMISTRY. 



Exp. b^. Fermentation Test. — Fill the ''fermentation- tube'* 
(Fig. 14) found in the desk with glucose solution; add a little 
yeast; insert stopper, with long arm of tube extending into 
glucose mixture nearly to bottom of tube, and allow it to stand 
upright, in a ivarm place, overnight. On the 
next day, test the gas, with which the tube is 
filled, with lime-water. 

Exp. 59. Phenylhydrazine Test. — Place about 
5 c.c. of glucose solution in a test-tube; add an 
equal volume of phenylhydrazine solution ; keep 
the tube in boiling water for tliirty minutes. 
Allow to cool gradually. Examine the precipi- 
tate microscopically and sketch the crystals. 

Disaccharids. — Exp. 60. Use dilute solutions 
of cane-sugar, milk-sugar, and maltose, and 
make on each Fehling's test (Exp. 54), Barfoed's; 
test (Exp. 57), and the phenylhydrazine test 
(Exp. 59). Sketch the different osazone 
crystals obtained. 

Exp. 61. To a dilute solution of cane-sugar 
add a few drops of dilute H2SO4 and boil for 
five minutes. Cool the mixture and make slightly alkaline 
with NaOH. With this solution perform Exps. 54-57 and 59. 
Explain results. 

Polysaccharids. — Exp. 62. Examine potato, corn, and wheat 
starch under the microscope. Sketch the granules of each in 
note-book, and, while still on the slide, treat with a dilute iodin 
solution. Note changes in appearance of granules. 

Exp. 63. Make some starch paste by rubbing 1 gram of 
starch to a smooth, thin paste with water; then slowly pour 
it into 100 c.c. of boiling water, stirring constantly. With this 
solution compare a 1% solution of dextrin and a solution of 
glycogen * as follows : 




* For the isolation of glycogen, see Appendix. 



FATS AND OILS. 177 

(a) Treat each by boiling with Fehhng's solution. 

(b) Add to 5 c.c. of each a few drops of tannic-acid solu- 
tion. 

(c) To each solution add a drop of iodin solution. Note 
color of mixture while cold. Heat nearly to boiling and allow 
to cool again, watching the color during process. 

(d) To 5 c.c. of each solution add twice its volume of 66% 
alcohol. 

(e) Tabulate results of the tests, and formulate method of 
distinguishing these three substances from one another. 

SECTION III.— FATS AND OILS. 

Natural fats and oils of animal or vegetable origin are mix- 
tures of several compound glyceryl ethers or esters (see page 
139), and by subjecting them to cold and pressure they may 
be separated into two portions, one solid with comparatively 
high melting-point, and the other liquid at ordinary tempera- 
ture. The solid portion is known as the stearopten, and the 
liquid as the eleopten, of the fat. Thus from beef-fat we may 
express a fluid eleopten consisting largely of olein, and obtain 
as a residue a stearopten, stearin. The stearopten of the vol- 
atile or essential oils are classed as camphors, on account of 
their resemblance to ordinary camphor. Menthol from oil of 
peppermint, and thymol from oil of thyme, are examples of this 
class of compounds, both of which are largely used in dental 
practice. 

Properties. — Fats are insoluble in water, easily dissolved by 
ether, chloroform, and carbondisulphid, less easily by alcohol; 
crystalUzing on evaporation of the solvent. (Plate VI, Fig. 5.) 
They are emulsified by mechanical subdivision of the fat glob- 
ules , in the presence of some agent which prevents their reunit- 
ing. The vegetable mucilages, soap, jelly, etc., are such emul- 
sifying agents. On exposure to the air, fats and oils are more 
or less easily oxidized, which causes a separation of the fat 



178 PHYSIOLOGICAL CHEMISTRY. 

acid. This produces an unpleasant odor or taste, and the fat 
is said to become rancid. (For saponification of fats see page 
140 and Exp. 67 below.) 

Physiology. — Fats are not digested to any appreciable 
extent until they reach the intestine; here they are broken 
up by a fat-splitting enzyme, emulsified, and to a slight extent 
saponified, after which they may be absorbed by the system 
(see Pancreatic Digestion). 

Experiments with Fats and Oils. 

Exp. 64. Test solubility of olive-oil in water, ether, chloro- 
form, and alcohol, carefully avoiding the vicinity of a flame. 

Exp. 65. Let one or two drops of an ether solution of the 
oil drop on a plain white paper, also an ether solution of a 
volatile oil found on side shelf. Watch behavior of the two 
oils, and report differences, if any. 

Exp. 66. Dissolve a little solid fat in warm alcohol and 
examine with the microscope, and micropolariscope the crystals, 
which separate on cooUng. 

Exp. 67. Saponification. — To about 2 grams of solid fat 
(butter or lard), placed in a narrow beaker, add 10 or 15 c.c. 
of alcoholic solution of potassium hydroxid. Allow the beaker 
to stand on the water-bath till the alcohol is entirely evapo- 
rated, then dissolve the resulting soap in water; filter if neces- 
sary to obtain a clear solution and make the following tests: 

(a) Add to a portion of solution a saturated solution of 
sodium chlorid. What takes place? 

(h) To another portion add a few cubic centimeters of a 
solution of calcium or magnesium chlorid. Explain the re- 
sults. 

(c) Pour the remainder slowly, and with constant stirring, 
into warm dilute H2SO4, and heat on the water-bath. AVhat 
is the result? Write the equation. Transfer the mixture to a 
filter-paper which has been moistened with hot water, and 



FATS AND OILS. 179 

-wash with hot water till all H2SO4 is removed. Reserve the 
filtrate. 

Exp. 68. Fatty acids. 

(a) Dissolve a portion of the above precipitate (67, c) by 
warming with strong alcohol. Test the reaction of the solu- 
tion. Examine the crystals, which separate upon standing, 
with microscope and micropolariscope. (Plate VI, Fig. 6.) 

(6) Add to a portion a few cubic centimeters of a strong 
Na2C03 solution, and heat till the fatty acids dissolve. Cool. 
What takes place? Explain the reaction. Reserve this. 

Exp. 69. Neutralize the filtrate of 67, (c), and evaporate 
almost to dryness on the water-bath. Extract with alcohol 
and evaporate. Note the taste. Heat another portion of the 
residue with a little powdered dry KHSO4 in a dry test-tube, 
and note the odor, which is due to acrolein, CH2 = CH-CH0. 
Fuse some borax and glycerine on a platinum loop: green 
bead. 

Exp. 70. Emnlsification. — (a) Put 1 to 2 c.c. of a solution 
■of sodium carbonate (0.25%) in a watch-glass, and place in 
the centre of a drop of rancid oil. The oil-drop soon shows a 
white rim, and a white milky opacity extends over the solution. 
Note with the microscope the active movements in the vicinity 
of the fat-drop, due to the separation of minute particles of 
oil (Gad's experiment) . 

(b) Take six test-tubes and arrange as follows: 

1. 10 c.c. of a 0.2% Na2C03 solution + 2 drops neutral oil. 

2. 10 c.c. of a 0.2% Na2C03 solution + 2 drops rancid oil. 

3. 10 c.c. of soap-jelly (see 68 h) warm + 2 drops neutral oil. 

4. 10 c.c. of albumin solution + 2 drops neutral oil. 

5. 10 c.c. of gum-arabic solution + 2 drops neutral oil. 

6. 10 c.c. of water + 2 drops neutral oil. 

Shake all the mixtures thoroughly and note the results. 
What conclusions do you form relative to the influence of 
conditions upon emulsification? 

(c) Examine a drop of an emulsion under the microscope. 



ISO PHYSIOLOGICAL CHEMISTRY. 



SECTION IV.— PROTEIDS. 



Protein or proteid substances are general terms used to 
designate the nitrogenized bodies which constitute the greater 
proportion of animal tissue. There have been many classifica- 
tions of the proteids, some based solely on their physical proper- 
ties, others based on what we know of their chemical composition. 
This latter method has the advantage of being the more scien- 
tific, but is not entirely satisfactory owing to our very limited 
knowledge. The most useful system at present is a combina- 
tion of both of the above methods. The following is after 
Hofmeister, ^'Ergebnisse der Physiologic," Jahrg. I. 

The following chemical groups have been isolated from 
the true proteid : 

I. Groups of the Aliphatic Series. 

A. Groups containing C, N, H. 

The only representative known is the guanidin radical 
(CNH)-NH2. 

B. Groups containing C, N, H, 0. 

1. Amido-acids. 

(a) Monamido-acids 

1. Monobasic monamido-acids, C„H2n+iN02. 

C2 is glycocoll. 

C3 is alanin. 

C5 is amidovalerianic acid. 

Ce is leucin, which occurs universally. 

2. Dibasic monamido-acids, CnH2n-iN04. 

C4 is asparaginic acid. 
C5 is glutaminic acid. 

(b) Diamido-acids (all monobasic acids). 

C2 is diamidoacetic acid (rare). 



PROTEIDS. 181 

Argynin (guanidin-a-amidovalerianic acid). Here the 
diamido-acid is combined with the guanidin radical, 

NH2NH.CNHCH2(CH2)2CHxNH2COOH. 

Lysin (a-e-diamidocapronic acid), 

iNH2CH2(CH2)3CHNH2COOH. 

2. Amido-alcohols. 

Glucosamin, C6lIii05(NH2), a hexose into which 
NH2 has entered the carbohydrate group of the 
proteid molecule. 
C. Groups containing C, N, H, 0, S. 

Cystein, amidothiolactic acid, CH2-Sn-CH(NH2) -COOH. 
Cystin, the sulphid of cystein, C6H12S2N2O4. 
a-thiolactic acid. 

II. Groups of the Aromatic Series. . 

A. Phenylalanin, CgHs-CHs-CHCNHo) -COOH. 

B. Tyrosin, C6H4 0H.CH2CH(NH2) COOH. 

III. 

A. Pyrrol group. 

CH-CH-CH-CHCOOH. 

1. a-pyrrolidin carbonic acid, I I 

' NH ' 

B. Indol group. 

1. Indol, see page 167. 

2. Skatol (methyl indol), see page 167. 

3. Tryptophan (indolamidopropionic acid), C11H12N2O2. 

4. Skatosin, C10H16N2O2. 

C. Pyridin group. 

Pyridin, see structural formula on page 166. 



182 PHYSIOLOGICAL CHEMISTRY. 

D. Pyrimidin group. 

Histidin : structural formula probably 

CH— NH 

II I 

C-N=CH 

I 

C-Ii2 

I 
CH-NH2 

I 

COOH. 

Excepting the carbohydrate group, and perhaps the pj^ridirt 
and pyrimidin groups, absent in a few special instances, all 
typical proteids contain at least one representative from each 
group. 

The further partial classification, based upon physical and 
chemical properties rather than chemical composition, has been 
adopted for the work, as follows : 



A. Simple Proteids. 

Albumin: Serum albumin, Egg-albumin, Lactalbumin (Myo- 

albumin) . 
Globuhn: Serum globulin, Fibrinogen, Myosinogen, Myoglobu- 

Un. 
Histon. 

B. Derived Proteids 

Through action of enzymes: Fibrin, Myosin. 

Through action of acids, etc.: Acidalbumin, Syntonin, Alkali- 
albuminates. 

Through action of digestive ferments: Proteoses, Albumose 
(Deutero-, Hetero-, etc.), Globulose, Myosinose, etc.. Pep- 
tones. 



PROTEIDS. 183 

C. Proteide, or Compound Proteid. 

Nucleoproteid : Nucleohiston. 

Nuclein. 

Glycoproteid : Mucin arid others. 

Nucleoglycoproteid. 

Chroinoproteid: Haemoglobins. 

D. PSEUDO-NUCLEOALBUAIIN. 

Casein: Ovovitillin. 

E. Albuminoids. 
Collagen. 
Elastin. 
Keratin. 
Reticulin and others. 

Albumins. 

The albumins are conveniently represented by egg-albumin 
and serum-albumin. They are soluble in water, respond to the 
general proteid reactions (Exp. 71, etc.), and may be completely 
precipitated by saturation of the solution by ammonium sul- 
phate. Albumin is coagulated by heat (75° to 80° C). 

Egg-albumin differs from serum-albumin in that it is not 
absorbed when injected into the circulation, but appears un- 
changed in the urine. Egg-albumin is readily precipitated from 
aqueous solution by alcohol, while serum-albumin is precipi- 
tated only with difficulty. Albumins in general form, with 
acids or with alkalies, derived albumins known as acid or alkaU 
albumin or albuminate. An acid albumin derived from myosin 
is known as syntonin. It differs but sUghtly from other acid 
albumins. The acid and alkali albumins are both precipitated 
by neutraUzation, but neither of them are coagulated by heat. 

If the hydrolysis of albumin is brought about by HCl at 
the body temperature, it causes the molecule to split into two 
proteids, one known as antialbuminate and the other as hemi- 



184 PHYSIOLOGICAL CHEMISTRY, 

albumose, these in turn becoming respectively antialbumid 
and hemipeptone. Sulphuric acid at a boiling temperature 
produces a similar change, except that the hemipeptone is fur- 
ther changed to leucin and tyrosin. Digestive ferments, 
pepsin, and trypsin produce antialbumose, hemiantipeptone, 
and hemialbumose, but trypsin alone converts the hemipeptone 
into leucin and tyrosin. 

Albumin normally occurs in all the body fluids except in the 
urine. The amount in milk is extremely shght; the amount in 
saliva seems to vary in inverse proportion to mucin. Albumin 
occurring in urine is always abnormal, although in the majority 
of cases it has no serious significance unless present in more 
than the shghtest possible trace. 

Globulin occurs associated with albumin in blood-plasma. 
It may be separated from it by half saturation with ammonium 
sulphate, which precipitates the globulin only, but it is not to 
be distinguished by the ordinary proteid tests and reactions. 
The albumin of albuminous urine always consists of a mixture 
of these two proteids, globulin and albumin, not, however, always 
in the same proportion. The globulins are not soluble in dis- 
tilled water as the albumins are, but a very small quantity of 
neutral salt, such as sodium chlorid, will serve to effect the 
solution. Globulin is thrown out of solution by action of carbon 
dioxid as a white flocculent precipitate. By dialysis the in- 
organic salts necessary for its solution will be removed and 
the proteid will be precipitated. It is also thrown out by 
saturation of sodium chlorid or magnesium sulphate. Globulin 
is coagulated by heat at practically the same temperature as 
serum-albumin, i.e., 75° C. 

General Proteid Reactions. 

Exp. 71. Test dried egg-albumin for C, H, S, and N, accord- 
ing to the methods described on pages 123 and 124. Test 
casein for phosphorus, and dried bLood for iron. 

There are several reactions which are common to nearly all 



PROTEIDS. 185 

proteids. For the following tests use a solution of egg-albumin 
(1/50) in water, as a general type of a proteid. 

1. Color Reactions. 

Exp. 72. Xanthoproteic Test. — To 10 c.c. of the solution add 
one third as much concentrated HNO3; there may or may 
not be a white precipitate produced (according to the nature 
of the proteid and the concentration). Boil; the precipitate 
or liquid turns yellow. When the solution becomes cool add 
an excess of NH4OH, which gives an orange color. (This color 
constitutes the essential part of the test.) 

Exp. 73. Milton's Test.— Add a few drops of Millon's re- 
agent* to a part of the albumin solution. A precipitate 
forms, which becomes brick-red upon heating. The Uquid is 
only colored red in the presence of non-coagulable proteid or 
minute traces of albumin. 

Exp. 74. Piotrowski's Test. — To a third portion add two 
drops of a very dilute solution of CUSO4, and then 5 to 10 c.c. 
of a 40% solution of NaOH. The solution becomes blue or 
violet. Proteoses and peptones give a rose-red color (biuret 
reaction) if only a trace of copper sulphate is used; an excess 
of CUSO4 gives a reddish-violet color, somewhat similar to that 
obtained in the presence of other proteids. This test responds 
with all proteids. 

2. General Precipitants. 

Proteids are precipitated from solution by the following 
reagents (peptones are exceptions in some cases) : 

Exp. 75. Acetic Acid and Potassic Ferrocyanid. — Make a por- 
tion strongly acid with acetic acid, and add a few drops of 
potassic ferrocyanid solution. A white flocculent precipitate 
is formed (not with peptones). 

Exp. 76. Alcohol. — Add one or two volumes of alcohol. 

* Mercuric nitrate in nitric acid. For the preparation of this and other 
reagents, see Appendix. 



186 PHYSIOLOGICAL CHEMISTRY. 

Exp. 77. Tannic Acid. — Make the solution acid with acetic 
acid, and add a few drops of tannic-acid solution 

Exp. 78. — Potassio-mer curie lodid. — Make acid another por- 
tion with HCl, and add a few drops of the reagent. 

Exp. 79. Neutral Salts. — Certain neutral salts precipitate 
most proteids. (NH4)2S04 added to complete saturation to 
proteid solutions, faintly acid with acetic acid, precipitates all 
proteids, with the exception of peptones. 

Experiments w^th Albumin and Globulin. 

The albumins and globulins respond to all the foregoing 
general reactions. 

Exp. 80. A specimen of solid egg-albumin, prepared by 
evaporating a solution to dryness at 40° C, is provided. Test 
its solubility in water, alcohol, acetic acid, KOH solution, and 
concentrated HCl. Report results. 

Perform the following additional experiments, using a dilute 
(1/10) solution of egg-albumin. 

Exp. 81. Nitric-acid Test. — Take 15 c.c. of the solution in a 
wine-glass, incline the glass, and allow 5 c.c. of concentrated 
HNO3 to run slowly down the side to form an under layer. 
What other proteids respond to this test? 

Exp. 82. Picric-acid Test. — Take a portion of the albumin 
solution and add a few drops of a solution of picric acid acidified 
with citric acid (Esbach's reagent). What other proteids re- 
spond to this test? 

Exp. 83. Action of (NH^)2S04.—To 10 c.c. of the albumin 
solution in a test-tube add some sohd (NH4)2S04, shaking 
until solution is thoroughly saturated. Allow to stand a Httle, 
shaking occasionally, then filter, saving the filtrate to test for 
albumin by the heat test. Report result. Test the solubility 
of the precipitate on the filter-paper. 

Exp. 84. Action of MgSO^. — Perform an experiment similar 
to Exp. 83, using solid MgS04 instead of (NH4)2S04. With 
what results? 



PRO TEWS. 187 

Exp. 85. Salts of the Heavy Metals. — Note the action of the 
following: AgN03, HgC^, CUSO4, Pb(C2H302)2. Use solutions 
of the salts and of albumin. 

Why is white of egg an antidote in cases of metallic poison- 
ing? 

Globulins. 

The following tests serve to distinguish the globulins from 
other proteids. The tests are made upon blood-serum, which 
contains an albumin (scrumalbumin) as well as a globulin 
(paraglobulin). 

Exp. 86. Action of CO2. — To 5 c.c. of the serum add 45 c.c. 
of ice-cold water. Place the mixture in a large test-tube or 
cylinder, surround it with ice-water, and pass through it a 
stream of CO2. A flocculent precipitate (paraglobulin) will be 
formed. 

Exp. 87. Precipitation by Dialysis. — Into a parchment dialyz- 
ing-tube, previously soaked in distilled water, pour 20 c.c. of 
the serum, swing the tube, with its contents, into a large vessel 
of distilled water, which is to be changed at intervals. Let 
stand twenty-four hours, then examine the serum in the dialyz- 
ing-tube; it will contain a flocculent precipitate of paraglobu- 
lin. Give explanation of cause of precipitation. 

Exp. 88. Pour serum, drop by drop, into a large volume of 
distilled water (in a beaker). What takes place? Explain. 

Exp. 89. Precipitation by Magnesium Sulphate. SsituYSite 
about 5 c.c. of the serum with magnesium sulphate. A heavy 
precipitate will be formed. Compare this with the action of 
the same salt on the egg-albumin solution. Paraglobulin is so 
completely precipitated by this salt that the method is used 
for its quantitative estimation. 



i 



188 PHYSIOLOGICAL CHEMISTRY. 

Albuminates. 
1. Alkali Albuminate. 

Exp. 90. To a solution of egg-albumin add a few drops of 
a 0.5% solution of NaOH, and warm gently for a few minutes. 
With the solution of alkali albuminate thus obtained perform 
the following tests: 

(a) Effect of Heating. — Boil some of the solution and report 
result. 

(6) Effect of Neutralizing.— Add a drop of litmus solution, 
and cautiously neutrahze. 

2. Acid Albuminate. 

Exp. 91. Add a small quantity of a 0.2% HCl solution to a 
solution of egg- albumin, and warm at 40° C. for one half to one 
hour. Or cover with an excess of 0.2% HCl some meat cut 
into fine pieces, and expose for a while to a temperature of 
40° C. Filter. With either of the solutions thus obtained 
make same tests, as on alkali albuminates, and compare results. 
How distinguish between them? 

The Proteoses (albumoses) may be considered as the next 
well-defined proteid product of proteid digestion following the 
albuminate. That is, leaving out the many intermediate 
products between which sharp lines of demarkation cannot 
be drawn, the decomposition of albumin brought about by 
enzymes or digestive ferments gives, first, acid albumin; second, 
albumose; and third, peptone. Albumose may be taken as a 
type of this second class of digestive products. Other pro- 
teoses, such as globulose, etc., are the substances derived from 
other proteids at a corresponding point of decomposition or 
peptic digestion. Albumose may be coagulated by heat at a 
temperature ranging upwards from 56° C, but, unlike albumin^ 
as the temperature approaches the boiUng-point the albumose 
goes again into solution, and at a boiling temperature may be 
separated from albumin by filtration. As the filtrate cools, 



PROTEIDS. 189 

albumose will again precipitate. The albumose is also pre- 
cipitated by nitric acid, by ferrocyanid of potassium and acetic 
acid (the precipitate in both cases being dissolved by heat)^^ 
and the other general proteid precipitates. The biuret test 
gives a distinctive color with proteoses and peptones, it being 
a marked reddish shade rather than the violet or blue obtained 
with other proteids. 

Peptones are the final products of peptic digestion of the 
proteids. They are soluble substances which give the biuret 
test similarly to the proteoses, but are not precipitated by heat, 
by nitric acid, by potassium ferrocyanid and acetic acid, nor 
by saturation with ammonium sulphate. 

Experiments with Albumose and Peptone. 

Albumoses (Hemialbumose). — This name includes four 
colsely allied forms of albumose, namely: (1) Protoalbumose; 
(2) Deuteroalbumose; (3) Heteroalbumose ; (4) Dysalbumose, 
an insoluble modification of heteroalbumose. Commercial 
peptone, which is substantially a mixture of albumoses and 
peptones, will be given out for use. 

Exp. 92. Make a solution in water, filter if necessary, and 
saturate with solid (NH4)2S04. Filter. The precipitate con- 
tains the albumoses, the filtrate the peptones. Reserve the 
filtrate for subsequent tests for peptone. Wash the precipitate 
with a saturated solution of ammonium sulphate; dissolve in 
water, and, with the solution obtained, perform the following 
tests, noting especially the tendency of albumose precipitates 
to dissolve upon the appHcation of heat and to reappear upoa 
coohng. 

Using this solution of albumose, repeat Exps. 72, 73, 74, 
81, 82. If no precipitate forms with HNO3 in Exp. 81^ 
add a drop or two of a saturated solution of common salt. 
(Deuteroalbumose gives this reaction only in the presence of 
HCl.) 



190 PHYSIOLOGICAL CHEMISTRY. 

Exp. 93. Saturate some of the solution with (NH4)2S04. 
Report the result. 

Exp. 94. To some of the solution add 2-3 drops of acetic 
acid, and then a saturated solution of NaCl. A precipitate 
forms, which dissolves on heating, to reappear on cooling. 

Exp. 95. Using the peptone solution prepared in manner 
above described from commercial peptone, repeat the experi- 
ments indicated in Exp. 92. 

Exp. 96. Effect of heating. — Boil some of the peptone solu- 
tion. Report the result. 

Exp. 97. Power of dialyzing. — Dialyze some of the peptone 
solution. Use 10 c.c. of the peptone solution, and in the out- 
side vessel about 100 c.c. of water, which in this case is not 
to be changed. After twenty-four hours test the outside water 
for peptone, employing the biuret test. 

Exp. 98. Action of Ammonimn Sulphate. — Saturate some of 
the peptone solution with solid (NH4)2S04. Report the result. 

A number of unknown solutions will be given out to be 
tested for carbohydrates and proteids. A report of the results, 
together with the methods employed, is to be made. 

Casein is the principal proteid found in milk. It exists 
in combination with calcium salts as caseinogen. This com- 
bination is broken up and the casein precipitated by the action 
of rennin and other enzymes, by acids, and by certain inorganic 
salts. 

Casein is classified as a pseudo-nucleo-albumin. The nucleo- 
proteids, so named because true nuclein may be obtained from 
them, are constituents of the cell nuclei, and differ in composi- 
tion from ordinary proteids by containing from 0.5 to 1.6% of 
phosphorus. Casein from cow's milk contains, according to 
Hammarsten, 0.85% of phosphorus. It is a pseudo-nudeo- 
albumin because, upon digestion with pepsin, pseudo-nuclein 
rather than true nuclein is obtained. 

Casein is practically insoluble in water, but dissolves readily 



PRO TE IDS. 



191 



in dilute alkaline solutions. Its precipitation as curd is de- 
pendent upon the presence of calcium salts. 

Lactalbumin is the only other proteid substance worthy of 
note in milk. This may be found in the filtrate after separat- 
ing the casein. The total proteids contained in human milk 
average from 1.5 to 2.5 per cent., while in cow's milk the 
proteids are 3.0 to 4.5 per cent. This difference, together with 
the variation of reaction and sugar-content, makes it necessary 
to ''modify" cow's milk when it is used as an infant food. 

The modification usually consists in the addition of lime- 
water (to change the reaction), of water (to reduce percentage 
of proteids), and of cream and milk-sugar (to increase fat and 
lactose) . 

The following table shows comparative composition: 



Human milk, 
Cow's milk. . 



Reaction. 


Total 
Solids. 


Proteids. 


Sugar. 


Fat. 


Alkaline 
Acid 


13.00% 
14.00% 


2.70% 
4.15% 


6.10% 
4.90% 


4.00% 
4.250/0 



Ash. 



.20% 
.70% 



Mucins have been classed as glycoproteids, indicating that 
by hydrolytic cleavage (from heating with dilute mineral acids) 
they will yield a simple proteid and a carbohydrate resembling 
glucose in its chemical reactions, particularly toward alkaline 
copper solutions. Other glycoproteids, many of which have 
been classified as mucins, are the mucoids, resembling mucin, 
and the chondroproteids, which yield chondroitin. 

The true mucins form a mucilaginous solution, and are 
precipitatedby acetic acid; contain C, H, N, S, and 0. Mucoids 
are not precipitated by acetic acid, while the chondroproteids 
may be. 

The ''mucin" obtained from tendons, and much used to 
study the physical properties of the mucins, is a chondroproteid. 
Mucin from the navel-cord is probably a true mucin, and fur- 
nishes the most convenient supply for laboratory investigations. 



192 PHYSIOLOGICAL CHEMISTRY. 

The mucin from the submaxillary gland is (according to Ham* 
marsten) also a true mucin, although the statement has been 
disputed. 

Mucin is not coagulated by heat, but responds to the general 
proteid reactions. It is of a faintly acid character and is 
combined with the alkaU or alkahne earth bases. Upon 
decomposition by dilute acids (hydrolysis) it yields a reducing 
substance and an acid albuminate; by further decomposition 
leucin, tyrosin, and Isevulinic acid are formed.* 

Experiments with Milk and Mucin. 

Exp. 99. Examine microscopically whole milk, skim-milk^ 
and cream. Note the relative amounts of fat in the three 
varieties. 

Exp. 100. Shake a little cream with chloroform in a test- 
tube; separate the chloroform, evaporate, and melt the fat 
residue obtained; allow it to cool slowly, when fat crystals will 
be obtained, which may be examined under the microscope and 
micropolariscope. 

Exp. 101. With a lactometer take the specific gravity of 
whole milk and skim-milk and explain the difference in results.. 

Exp. 102. Test the reaction of milk with Htmus. 

Exp. 103. Dilute some milk with six or seven times its 
volume of water, and add acetic acid drop by drop till the 
casein is precipitated. Filter and reserve the precipitate. Test 
the filtrate for proteids, if any remain; determine if possible 
their character. 

Exp. 104. Test another portion of the filtrate for carbohy- 
drates, determining the variety present. 

Exp. 105. To 50 c.c. of milk add a few drops of rennin 
solution; keep at a temperature of 40° C. for a few minutes 
and explain results. 

Exp. 106. Take a portion of the precipitated casein from 

* Simon, Physiological Chemistry. 



BLOOD, BONE, MUSCLE, ETC. 193 

Exp. 103, digest at 40° C. with pepsin IICl for twenty minutes 
or half an hour. While digesting, test other portions of casein, 
for solubility in water, in dilute acid and dilute alkaU. Test 
also a portion for phosphorus by boiling in a test-tube with 
dilute nitric acid, cooling to at least 50° C. and adding ammo- 
nium molybdate solution. 

Exp. 107. To a little skim-milk contained in a test-tube add 
a saturated solution of ammonium sulphate. 

Exp. 108. To a solution of mucin found on the side shelf * 
add acetic acid till precipitation takes place. Settle, filter, 
wash, and test solubility in water; dilute alkali solution and 
5% PICl. 

Exp. 109. Make color-tests for proteids. 

Exp. 110. Boil a httle nmcin solution with dilute HCl for 
several minutes. Cool, neutrahze, and test for sugar. 

SECTION v.— BLOOD, BONE, MUSCLE, ETC. 

Blood. 

The blood, carrying oxygen and other forms of nutrition to 
all parts of the body, and returning carbon monoxid and the 
waste products of cellular activity, is an exceedingly complex 
substance. The composition of the blood itself, however, may 
be grossly described as a fluid (plasma) carrying in suspension 
the cellular constituents, red and white corpuscles. The plasma 
contains sohd matter to the extent of about 8.9%. This is 
largely proteid, consisting of serum globulin, serum albumin, 
a shght amount of nucleoproteid, and fibrinogen; also a fibrin 
ferment, thrombase or thrombin, by the action of which the 
fibrin is separated as a ^'clot" which mechanically carries down 
the corpuscles. As the clot contracts, the ^' serum" separates 
as a clear, amber-colored liquid, consisting of serum globulin 
(paraglobuUn), serum albumin, and the fibrin ferment. 

* For preparation of mucin solution see Appendix. 



194 PHYSIOLOGICAL CHEMISTRY. 

Fibrin.— The fibrin may be obtained free from corpuscles 
by whipping the fresh blood. Under this treatment the fibrin 
separates as shreds, while the remaining constituents constitute 
the " defibrinated blood." The presence of hme-salts is essential 
to the coagulation of the blood, i.e., the decomposition of the 
fibrinogen and separation of fibrin, in much the same way as in 
the decomposition of caseinogen and precipitation of casein 
from milk. 

Fibrin, as usually obtained, is in the form of brown, stringy, 
and ''fibrinous" masses, and is kept for laboratory use under 
glycerine. It is insoluble in water or alcohol. In dilute acid 
(HCl) or alkali solutions, it swells and ultimately dissolves, 
although it may be several days before solution is effected. 
The fibrins from the blood of different animals differ in com- 
position, as indicated by marked differences in solubility. 

The chemistry of the red and white corpuscles is more complex? 
and not so well known as the chemistry of the plasma, which 
we have considered. The red corpuscles consist of a frame of 
protoplasm, also called stroma, which contains lecithin, choles- 
trin, nucleoalbumin, and a globulin. (Hammarsten.) Upon 
and all through the stroma is the haemoglobin, which, together 
with its oxygen compound oxyhsemoglobin, is responsible for 
the color of the blood. Oxyhsemoglobin may be obtained as 
silky, transparent crystals of blood-red color. 

From haemoglobin may be derived the blood pigment hcemo- 
chromogen, containing iron, and this by oxidation is converted 
mto hsematin. The iron from the blood may, by decomposi- 
tion of the pigment and subsequent combination with sulphur 
(FeS), cause discoloration of teeth. This is the theory of 
Dr. Kirk of Philadelphia, and in the author's opinion is per- 
fectly sound, and far more probable than other explanations 
which have been offered, but which do not recognize the forma- 
tion of a sulphur compound. 

CO Haemoglobin. — Haemoglobin forms with carbon monoxid 
(from water-gas or other sources) a definite and very stable 



BLOOD, BONE, MUSCLE, ETC. 195 

compound, being even stronger than the oxyhsemoglobin, to 
which reference has previously been made. Blood containing 
carbon nionoxid hirnioglobin is of a bright-red color, which 
darkens in the air much more slowly than ordinary blood. 

Haemin, or Teichmann's ha^min crystals, is the hydrochloric 
acid compound of ha^matin. (See Exp. 115.) 

The form of the red corpuscle is that of a biconcave disk 
without nucleus; by action of water it becomes swollen, and 
the haemoglobin may be washed away, leaving the ''stroma." 
The diameter of the red corpuscles of human blood is about 
•sinTTT ^^ ^^ inoh. Of the domestic animals, the corpuscles of 
the dog approach most nearly to this measurement of the 
human. The sheep, horse, and ox have smaller corpuscles 
than man, while those of birds, cold-blooded animals, and 
reptiles are larger. (See Plate VII, Figs. 5 and 6.) 

The white corpuscles are rather larger than the red, and 
occur in much smaller numbers, a cubic millimeter containing 
about 5,000,000 red to 7,500 white. The white corpuscles pre- 
sent a much greater diversity of character than do the red. 
They contain one to four nuclei, and are capable of amoeboid 
movements. The white corpuscles are also called leucocytes, 
aggregations of which constitute pus. The leucocytes are di- 
vided histologically into various classes, — lymphocyte, neutro- 
philes, eosinophiles, etc., — according as they are acted upon by 
different staining-fluids or fulfill some particular office; but 
these are not to be distinguished chemically. 

Bone. 

If all organic matter is burned off from bone, there remains 
the bone-earth, so called, made up of the phosphates and car- 
bonates of lime and magnesia, with sHght amounts of chlorin, 
fluorin, and of sulphates, the proportion being practically 
the same as given for dentine, under Teeth, on page 119. Be- 
cause in some diseases, in which the bones are softened or decal- 
cified (as osteomalacia), the relation of the CaO and P2O5 



196 PHYSIOLOGICAL CHEMISTRY. 

remains unchanged, it has been claimed that these substances 
exist in the bone in the form of a definite phosphate-carbonate 
containing three molecules of the tribasic phosphate to one of 
carbonate: 3Ca3(P04)2.CaC03. 

If, by treatment with dilute hydrochloric acid, the min- 
eral constituents are entirely dissolved out of bone, there re- 
mains a substance from which glue (gelatine) is derived, of 
similar composition to collagen, from connective tissue, and 
known as ossein. Neither of these (ossein or collagen) are 
soluble in water or in dilute acids. 

Gelatine is made by hydrolysis of ossein or collagen brought 
about by prolonged boiling with dilute mineral acids. Gelatine, 
if first treated with cold water till soft, may be dissolved in 
hot water. The solution is precipitated by mercuric chlorid, 
alcohol, tannic and picric acids. It responds but feebly to the 
general proteid reactions, but, by digestion with either pepsin 
or trypsin, compounds are obtained analogous to those result- 
ing from similar proteid digestion. 

Experiments on Blood and Bone. 

Exp. 111. Test the reaction of blood with a piece of litmus- 
paper which has been previously soaked in a concentrated 
NaCl solution. To what is reaction due? 

Exp. 112. Blood-corpuscles.— {a) Examine a drop of blood 
under the microscope. Sketch the red and white corpuscles. 

(b) Note the difference between the corpuscles of mammals 
and those of birds and reptiles. 

(c) Note the effect upon the red corpuscles produced by the 
addition of (1) water, (2) a concentrated solution of salt. 

Exp. 113. Hcem-oglohin Crystals. — Place a drop of defibrinated 
rat's blood on a slide; add a drop or two of water; mix, and 
cover with a cover-glass. Sketch the crystals which separate 
after a few minutes. Or add a few drops of ether to some 
blood in a test-tube; shake thoroughly until the blood becomes 
'Maky," and then place the tube on ice till crystals appear. 



BLOOD, BONE, MUSCLE, ETC. 197 

Exp. 114. A spectroscope will be found ready for use in the 
laboratory, and the absorption-bands given by oxyha^moglobin 
and haemoglobin will be demonstrated. The student may 
prepare solutions for examination as follows: 

(a) Oxyhccmoglobin.—\Jsc dilute blood (one part of de- 
fibrinated blood in fifty parts distilled water). 

(h) Hwmoglohin (reduced haemoglobin).— Add to blood a few 
drops of strong ammonium sulphid, or one or two drops of 
freshly-prepared Stokes's reagent.* Note the change in color 
produced by the addition of the reducing agent. Shake with air 
and note the rapid change to oxyhaemoglobin. 

(r) Hoemochromogen. — To a little of the hsemochromogen, 
reduced with ammonium sulphid, add a few drops of concen- 
trated NaCl, and note the spectrum of reduced hsematin or 
hsemochromogen . 

(d) Carhonmonoxid Hoemoglohin. — Pass a current of illu- 
minating-gas through a (Ulute oxyhaemoglobin solution for a 
few minutes and filter. Note the change of color. Try the 
effect on the solution of (1) ammonium sulphid; (2) Stokes's 
reagent; (3) shaking with air. Note the stability of the com- 
pound. 

Exp. 115. Hcemin Crystals (Teichmann^s Test). — Place a bit 
of powdered dried blood on a glass sHde; add a minute crystal 
of NaCl (fresh blood contains sufficient NaCl) and two drops 
of glacial acetic acid. Cover with a cover-glass and warm gently 
over a flame until bubbles appear. On cooling, dark-brown 
rhombic crystals, often crossed, separate (chlorid of hsematin). 
Similar crystals can be obtained by using an alkaline iodid or 
bromid in place of NaCl. 

Exp. 116. Coagidation of Blood. — Observe the phenomena of 
coagulation as it takes plase (a) in a test-tube, (h) in a drop 
of blood examined under the microscope. Explain fully. 

* Stokes's reagent consists of two parts of ferrous sulphate and three parts 
of tartaric acid dissolved in water and ammonia added to distinct alkaline reac- 
tion. There should be no permanent precipitate. 



198 PHYSIOLOGICAL CHEMISTRY. 

Exp. 117. Proteids of Blood-plasma. — (a) Serum-albumin. 
(6) Serum-globulin. Using blood-serum, separate and identify 
these two proteids. 

(c) i^i6rmo^en.— Fibrinogen is a globulin found in blood- 
plasma, lymph, etc., together with paraglobulin. Like para- 
globuhn it responds to all the general precipitants and tests, 
and in addition gives the reactions with CO2, dialysis and 
MgS04. It is distinguished from paraglobulin easily by two 
reactions, viz., its power to coagulate, i.e., to form fibrin 
when acted on by fibrin ferment, and its temperature of 
heat coagulation, which wdll be found to be from 56° to 
60° C. 

Exp. 118. Fibrin. — (a) Note its physical properties. 

(6) Note action of 0.2% hydrochloric acid. 

(c) Apply the proteid color tests. 

Exp. 119. Examine microscopically and sketch structure of 
bone and teeth. 

Exp. 120. Gelatin. — Take about 10 grams of bone, prefer- 
ably small pieces of the shaft of a long bone, clean carefully, 
and allow to stand for a few days in 60 c.c. of dilute HCl (1/20). 
The dilute acid dissolves the inorganic portion of the bone, 
leaving the collagen. Note the effervescence due to the pres- 
ence of carbonates. The acid solution is poured off and kept 
for further investigation. The remains of the bone are allowed 
to stand overnight in a dilute solution (1/10) of Na2C03, and 
then boiled in 100 c.c. of water for an hour or two. The col- 
lagen undergoes hydration and is converted into gelatin, which 
dissolves. A core of bone untouched by the acid usually 
remains. Evaporate the solution to 25 c.c. bulk, and allow 
to cool. A firm jelly is formed if the solution is sufficiently 
concentrated. If the solution gelatinizes, add an equal bulk 
of water and heat anew. With the solution perform the fol- 
lowing experiments. (If too little gelatin is obtained for all 
the tests, a solution will be provided.) 

Gelatin may also be prepared from tendons which consist 



BLOOD, BONE, MUSCLE, ETC, 199 

almost wholly of white fibres. Collagen is the substance of 
which white fibres are made up. 

Exp. 121. With a solution of gelatin make the usual tests 
for proteid. 

Exp. 122. Precipitate gelatin from dilute solution with the 
following reagents : 

{a) Tannic acid. 

(6) Alcohol. 

(c) Acetic acid and potassium ferrocyanid. 

{d) Mercuric chlorid. 

(e) Picric acid. 

Muscle. 

The chemistry of muscle is complex. It changes rapidly 
upon the death of the animal, so much so that the liquid which 
may be expressed from living muscle (or from muscle frozen 
immediately upon the death of the animal) has been called 
muscle plasma, in distinction from the fluid obtained in the 
same manner from dead muscle, which is called muscle serum. 
The chemical reactions of these solutions differ, due to the 
formation of sarcolactic acid in the dead muscle. The pro- 
teids differ in certain respects. Myosin is the most essential 
constituent of muscle plasma, and corresponds to the fibrin 
of the blood-clot. It exists as a parent proteid myosinogen, 
or myogen, from which it may be precipitated by saturation 
with salt or magnesium sulphate. Myosin has many of the 
properties of the globulins, but differs in the very important 
particular of not being precipitated by dyalization. Among 
the more important extractive bodies obtained from muscle are 
creatin, carnin, inosite, glycogen, and lactic acid. Creatin is a 
xanthin body, being chemically a methyl-guanidin-acetic acid, 
which may appear in the urine as creatinin. (Great inin is crea- 
tin minus H2O.) 

Carnin is a white crystalline substance obtained from meat 
extract and converted by oxidation by nitric acid, chlorin or 



200 PHYSIOLOGICAL CHEMISTRY. 

bromin into hyopxanthin or sarkin. Its chemical constitution 
is not postively known. 

Inosite, C6H12O6 + H2O, is a hexahydroxy benzene, 
C6H6(On)6 + H20. It has a sweet taste, and was formerly 
erroneously classed with the carbohydrates. - It is capable of 
yielding lactic and butyric acids(?). 

Glycogen occurs in slight amounts in muscle, but decomposes 
after death, with formation of a reducing sugar. (Compare 
page 174.) 

Lactic Acid is a constituent not only of muscle but also of 
various glands, of the bile, and of blood. For the chemistry 
of this substance, see page 146. 

Keratin. 

Keratin is the characteristic constituent of the hair, nails, 
feathers, and horn. It contains a considerable proportion of 
loosely combined sulphur. It is insoluble in dilute acids and 
unaffected by any of the digestive ferments; it does, however, 
dissolve in the caustic alkali solutions, and may be used as 
the source of leucin, tyrosin, cystin, and other well-known 
products of proteid digestion. 

Experiments with Muscle and Keratin. 

Exp. 123. Place 25 grams of fresh finely chopped muscle 
in a beaker with 75 c.c. of 5% solution of common salt, and 
allow to stand for about one hour, with frequent stirrin . In 
the meanwhile perform Exp. 124. Then filter off the liquid 
and make the following tests with the filtrate : 

(a) Test for proteids. 

(b) Having found proteids, pour a Httle of the solution into 
a beaker of water. Result. Inference (myosin). 

(c) Make a fractional heat coagulation in the following 
manner (upon the care with which the temperatures given are 
adhered to, depends the success of the separation) : Warm to 



BLOOD, BONE, MUSCLE, ETC. 201 

44^-50° C, and keep at that temperature for a few minutes. 
The coagulum is myosin [synonyms: paramyosinogen (Halli- 
burton), nmscuUn (older authors)]. In solutions the myosin, 
which has the properties of a globulin, becomes insoluble after a 
time, because it changes to myosinfibrin. In heating the solu- 
tion as above, a slight cloud may appear at 30°-40° C. This 
is due to soluble myogenfibrin. Now filter off the coagulated 
myosin. 

Heat filtrate to 55°-65° C. The coagulum is myogen 
(synonym: myosinogen). In spontaneous coagulation of its 
solutions it forms, first, soluble myogenfibrin, and, finally, in- 
soluble myogenfibrin. Filter. 

Heat to 70°-90° C. Coagulum is serum albumin from the 
blood within the nmscle, and is not a constituent of the muscle 
plasma. Filter. 

Test filtrate for proteids. If it shows a slight biuret test, 
this is due either to incomplete precipitation by coagulation 
or to the post-mortem formation of albumose or peptone by 
auto-digestion (autolysis). 

Exp. 124. Make an aqueous extract of muscle, and test for 
lactic acid by acidulating with H2SO4, extracting with ether 
and testing the ethereal extract with very dilute ferric chlorid 
solution. The presence of lactic acid is shown by a bright- 
yellow color. 

Exp. 125. Creatin may be most conveniently prepared from 
a strong solution of Liebig's extract. Dissolve the extract in 
twenty parts of water and remove excess of lead; concentrate 
to a fine syrup over a water-bath and allow to stand in a cool 
place, when creatin crystals will separate out. Two or three 
days' time may be required before the crystals are obtained. 
They may be washed with 88% alcohol and purified by re- 
crystallization from water. Hypoxanthin and sarcolactic acid 
may be obtained from the mother liquor.* 

* Lea's Chemical Basis of the Animal Body. 



202 - PHYSIOLOGICAL CHEMISTRY. 

Exp. 126. Creatinin may be prepared from creatin by 
boiling for ten or fifteen minutes with very dilute sulphuric acid. 
Neutralize the acid with BaCOs, evaporate and filter to dryness 
on a water-bath, and extract the creatinin with alcohol. Upon 
evaporation the creatinin is obtained in the form of crystals. 

Keratins are characterized by their insolubility, and by their 
high content of loosely combined sulphur. 

Exp. 127. Test solubiUty of keratin (nail or horn) in water, 
acids, alkaUes, gastric and pancreatic juice. 

Exp. 128. Warm a bit of keratin with 5 c.c. strong NaOH 
solution for a few minutes, and add a few drops of a lead acetate 
solution. What is the result? 



PART VII. 

DIGESTION. 



SECTION I.— SALIVA: PROPERTIES AND CONSTITUENTS. 

The saliva is a mixed secretion from the parotid, submax 
illarV; and sublingual glands, together with a shght amount 
obtained from the smaller buccal glands. The chemical com- 
position of the secretion from these various sources differs con- 
siderably, but from a chemical standpoint we are nmch more 
interested in the mixed sahva and its constituents than the 
differences in the product of the various glands. The notable 
differences are that the mucin is practically wanting in the 
parotid saliva. The alkaline salts seem to be in smaller pro- 
portion in the parotid saliva than in the other two. Potassium 
sulphocyanate is a constituent of all varieties of saliva, although 
more constantly present in the submaxillary and in the sub- 
lingual than in the parotid. The parotid, on the other hand, 
contains a larger proportion of dissolved gases. The data on 
the composition of these varieties differ to a considerable ex- 
tent and comparisons are not wholly satisfactory. 

The mixed saliva contains, according to Professor Michaels, 
all the salts of the blood which are dializable through the 
salivary glands, and hence furnishes a rehable index of meta- 
bolic processes which are being carried on within the system. 
In order for this fact to be of practical value, two things are 
obviously of prime importance: First, methods of analysis 

203 



204 DIGESTION, 

which are not too complicated and at the same time conclu- 
sive; second, a knowledge regarding the source of the various 
constituents found which will enable us to make a rational 
interpretation of the results obtained. In both of these fun- 
damentals we are ver}^ much hampered by lack of knowledge; 
as yet there is much to be desired in the way of practical clin- 
ical tests for the various salivary constituents, and very much 
to be learned as to their meanings in order to make deductions 
which shall be conclusive. We are led to believe from the work 
of Professor Michaels and Dr. Kirk that this subject of saHvary 
analysis promises much, and is certainly worthy of careful 
investigation. 

The quantity of saliva secreted in twenty-four hours is 
variously estimated from a few hundred to 1500 c.c; 1200 to 
1500 is the more probable amount. The quantity is dimin- 
ished in fevers, severe diarrhoea, diabetes, and nephritis, by 
fear and anxiety, and by the use of atropine. It is increased 
by smoking, by mastication, by the use of mercury, potassium 
iodid, or pilocarpin. The flow of sahva is also increased by 
action of the sympathetic nervous system, during pregnancy, 
and by local inflammatory process. 

Physical Properties. — The physical properties of saliva 
include its appearance, specific gravity, reaction, color, and 
odor. 

Appearance. — The appearance is clear, opalescent, frothy, 
or cloudy; normal saliva is usually opalescent. It may become 
turbid by precipitation of lime-salts caused by the escape of 
carbon dioxid. 

Specific Gravity. — Specific gravity ranges from 1002 to 1009, 
the total solids being only from 0.6 to 2.5 per cent. 

Reaction. — The reaction is normally alkaline to litmus- 
paper or to lacmoid. Normal saliva, however, fails to give 
an alkaline reaction with phenolphthalein due to the presence 
of free CO2, which may be present to the extent of 19 parts in 
100, by volume. If the sample be subjected to even a slight 



SALIVA: PROPERTIES AND CONSTITUENTS. 205 

degree of heat the acid gas is expelled; then the usual pink color 
may be obtained with this indicator. Saliva mey be acid upon 
fasting, particularly before breakfast and also after much 
talking. Acid conditions may exist which are local in their 
character and due to lactic acid fermentation. Acid salivas 
may also be met with in cases of rheumatism, mercury saliva- 
tion, and diabetes. By exercise of the glands, as during the 
chewing of food, the alkalinity is increased; oftentimes the 
reaction changes from faintly acid to alkaline during this pro- 
cess, the proportion of alkaline salts becoming greater, although 
the total solids as a whole are slightly diminished. This fact 
of the change in the reaction from acid to alkaline has been 
explained by ascribing the acidity due to fermenting particles 
in the mouth ; and the continued process of chewing and swal- 
lowing washes this away, or, in other words, that the change 
in reaction is a mechanical one rather than a change of the 
chemical composition of the secretion. This explanation seems 
to be a superficial one and without sufficient experimental 
foundation. 

Color. — SaUva is usually colorless when fresh, but upon 
standing for twenty-four hours may assume various tints, 
which are developed from constituents derived from bile. 
(Professor Michaels.) Saliva may be colored red or brown by 
the presence of blood or blood pigments, but in such cases the 
source of the color is usually local and easily discovered. 

Odor. — Normal saliva is practically odorless. In cases of 
pyorrhoea there is usually a peculiar fetid odor easily recog- 
nized. In other pathogenic conditions the odor may be 
slightly ammoniacal, or occasionally resemble the odor of 
acetone or garlic. 

Constituents. — We should here distinguish carefully be- 
tween saliva proper and sputum. The constituents of sputum 
are derived from the air-passages rather than from the salivary 
glands, and are not at present under consideration. Among 
the normal constituents of saliva are included mucin, albumin. 



206 DIGESTION. 

ptyalin, ammonium salts, potassium sulphocyanate, alkaline 
phosphates, and chlorids, with traces of carbonates; and, in 
the sediment, epithehum cells, occasional leucocytes, and fat 
globules. The abnormal constituents will include glycogen, 
urea, dextrin, rarely sugar, cholesterin, derivatives from bile, 
lecithin, xanthin bodies or alkaline urates, acetone, lactic acid, 
and crystalline elements resulting from insufficient oxidation 
or perverted glandular function. These latter are recognizable 
by the micropolariscope. Mercury and lead may also be found 
in saliva in cases of poisoning by salts of these metals. 

Mucin. — The secretion from the parotid gland contains 
practically no mucin, but the sublingual sahva contains large 
amounts. Mucin is, according to Simon, the most important 
constituent of the saliva, not excepting ptyalin. The various 
glands contributing salivary mucin do not in all probability 
furnish just the same kind of proteid; moreover, the mucin 
from different individuals seems to vary in composition and 
properties, some yielding more abundant acid decomposition 
products than others (see article by W. D. Miller in Dental 
Cosmos for November, 1905), while, according to Professor 
Michaels, the mucin varies much in the same individual in 
health and disease. The changes in the characteristics of 
salivary mucin is an almost unexplored field of dental research, 
and the importance of these changes, as indications of diathetic 
states, promises much. 

An excess of mucin in the saliva tends to an increase of 
bacterial growth, from the fact that it furnishes increased 
facilities for multiplication; it may also give rise to mucic acid, 
which, according to Dr. G. W. Cook of Chicago, is a probable 
factor in tooth erosion. (See Dental Review, May 1906, p. 461.) 

Albumin. — Albumin is present in very small quantities 
increased during mercurial ptyaUsm, usually in cases of pyor- 
rhoea, and, according to some authorities, in various albuminu- 
rias. It may be detected by usual methods after the separa- 
tion of mucin. 



SALIVA : PROPERTIES AND CONSTITUENTS. 207 

"According to Vulpian, the quantity of albumin is increased 
in the saliva of albuininurics of Bright's disease. The saliva 
of a patient with parenchymatous nephritis had mucin 0.253 
and albumin 0.182 per cent. The saliva of another patient, 
with albuminuria of cardiac origin, contained mucin 0.45, 
albumin 0.145 per cent. In a healthy man there was found 
mucin 0.320, albumin 0.05 per cent. This fact has been con- 
firmed by Pouchet, who found these substances in greater 
quantities." * 

Ptyalin. — Ptyalin is the principal ferment of the saliva; it 
converts starch, by hydrolysis through the various dextrins, 
(page 173) to maltose. The maltose in turn being converted 
into glucose by a second ferment, known as maltase, which 
exists in saliva in very small (luantities. 

The activity of ptyaUn is greatest at a temperature of 40° C. 
Very faintly acid saliva is the best media. Neutral and faintly 
alkaUne saUvas are next in order. 

The amylolytic power of a given sample of saliva may be 
determined by the action on dilute starch paste. In making 
comparative tests it is essential that the conditions under which 
the ptyalin is allowed to act should be exactly the same, espe- 
cially as regards the temperature and duration of the process. 
A slight variation in the strength of the starch solution is of 
no consequence, as starch is supposed to be in excess. (See 
Exp. 130.) 

Ammonium Salts. — Ammonium salts occur chiefly as chlorid, 
probably to some extent as sulphocyanate, and occasionally as 
oxalate. Professor Michaels says that ammonia must be con- 
sidered as a more completely oxidized form of nitrogen than 
urea, hence its relative increase is observed in all diseases which 
occasion an excess of nitrogen and urea, as in tuberculosis and 
all hypoacid diatheses. There is a decrease of ammonia when- 
ever the nitrogen fails to reach the stage of oxidation repre- 

* Dr. Joseph P. Michaels. S. S. White's reprint of paper read before Inter- 
national Dental Congress, Paris, 1900. 



208 DIGESTION. 

sented by urea. This condition is accompanied by uric acid 
and other products of deficient oxidation, and characterizes the 
hyperacid state. The ammonia may be detected by a micro- 
scopical examination of the dried sahva, although the ammo- 
nium salts do not polarize light (Plate VIII, Fig. 1), also by 
the reaction with Nessler's reagent, which produces a yellow 
color. 

Potassium Sulphocyanate is peculiarly a constituent of the 
saUva, although it occurs in traces in the blood, urine, etc.. 
In a state of health, according to Dr. Michaels, the ammonium 
salts and the sulphocyanates are present in very slight amounts^ 
and the color-tests, with Nessler's solution and with ferric chloride 
respectively, are of about equal intensity. In the hyperacid 
state the sulphocyanates are in excess of ammonia, while in 
hypoacid conditions, the ammonia exists in the greater quan- 
tity. Sulphocyanate is detected by means of ferric chlorid,. 
and distinguished from meconates and acetates, as indicated 
by Exp. 131. The sulphocyanates are normal constituents of 
saliva, and consequently always present. According to A. 
Mayer (Deutsch. arch. f. kUn. med.. Vol. 79, No. 394), the 
sulphocyanates, without doubt, result from the decomposition 
of proteids, and exist in the urine in quantities variously esti- 
mated from 20 to 80 milligrams per liter, while in saliva it has 
been estimated as 60 to 100 milligrams per liter. Professor 
Ludholz of the University of Pennsylvania says that the sul- 
phocyanates are eliminated in increased amounts in conditions 
where there is a lack of oxygen in the system, thus corrobor- 
ating statements of Professor Michaels (see Ammonia). Dr. 
Fenwick (Lancet, 1877, Vol. II, page 303) demonstrated that 
the quantity of KCNS was directly dependent upon the bile 
salts in the blood. He found an increase of the salt in liver 
disorders attended with increase of bile salts in the blood, and 
marked increase in jaundice. In gout, rheumatism, and con- 
ditions producing pyorrhoea it is also claimed to be present in 
considerable quantity. 



SALIVA: PROPERTIES AND CONSTITUENTS. 209 

Phosphates and Carbonates. — These salts are probably pres- 
ent in both acid and neutral forms; that is, the phosphate may 
exist as Na2HP0.i also as NaH2P04, and at times both of these 
may be present at once. The acid carbonate, NaHCOs, is an 
undoubted constituent, while the neutral carbonate is present 
in only very slight quantities, if at all. Chittenden says that 
human mixed saliva contains normally no sodium carbonate 
whatever. 

As explained by Dr. Kirk, the normal reaction by which 
over-acidity of the blood is taken care of by renal epithehum 
is H2C03 + Na2HP04 = NaH2P04 + NaHC03, and when condi- 
tions are such as to produce larger quantities of carbonic 
acid than the kidneys can eliminate in accordance with the 
above reaction, there is an increased acidity of the sahva as 
well as of the urine.* In the hypoacid individual, the so-called 
alkaline sodium phosphate, Na2HP04, is present in the greater 
quantity. In diabetic patients sugar has very rarely been 
found in the saliva; one case coming under the observation of 
the author was that of a woman of middle age, with diabetes 
of long standing, with 8% of sugar in the urine, and there was 
obtained a very few osazone crystals by subjecting a consider- 
able quantity of saliva, after concentration, to the phenyl- 
hydrazine test. 

Urea has been repeatedly found in the saliva of patients 
suffering from chronic nephritis. 

Acetone is of quite frequent occurrence in the saHva. In 
diabetic patients this substance is often present in compara- 
tively large amounts, sometimes sufficient for the detection of 
the acetone by its characteristic odor. In the experience of 
the author acetone may appear in the saliva when it is not 
present in the urine. In such cases it has usually resulted 
from disordered digestion and a consequent faulty metabohsm. 
(For further consideration of acetone, see Urine.) 

* International Dental Journal, February, 1904. 



210 DIGESTION. 

Chlosterin and lecithin have been found by Professor 
Michaels in pathological saliva, and leucin has been found by 
Michaels in a case of lupus and, according to Novey, in a 
case of hysteria. 

Of the crystalline salts which may be separated by evap- 
oration of dialyzed saliva, the sodium oxalate and the lactates 
or lacto-phosphates of lime and magnesia are of the most 
importance, and have been the most thoroughly studied. As 
these salts may likewise be separated from urine their signifi- 
cance will be studied under that head. 

SECTION II.— ANALYSIS OF SALIVA. 

In the systematic examination of saliva the first thing to 
be done is to start a few cubic centimeters dialyzing (page 21 2) 
for subsequent examination of crystals by polarized fight. 
'^The five-drop test" of Professor Michaels may next be made 
as follows : On a porcelain tile place 5 large-sized drops of the 
saHva under examination. 

Sulphocyanate Test. — To the first drop add one drop of 5% 
ferric chlorid, shghtly acid with HCl; a reddish coloration con- 
stitutes the test for sulphocyanates. (For properties of ferric 
sulphocyanate, see Exp. 131, page 215). 

Ammonium Salts. — To the second drop add one drop of 
Nessler's reagent: a yellow to brown shows the presence of 
ammonium salts. If a precipitate forms by the addition of 
Nessler's reagent, it indicates either a large amount of ammonia 
or the presence of urobiHn. If due to urobilin the precipitate 
is of a rose color after desiccation. Ammonium salts are 
usually seen in the evaporated drop examined by polarized 
light. Plate VIII, Fig. 1. 

Chlorids. — To the third drop add a small drop of a 5% 
solution of neutral chromate of potassium, K2Cr04. Mix 
with a glass rod, and add one drop of a 1/10% solution of silver 
nitrate. This constitutes the chlorin test which, if present in 
normal quantities, will give a reddish precipitate, gradually 



• ANALYSIS OF SALIVA. 211 

becoming white. Should the precipitate remain red it shows 
the chlorin deficient or less than normal in amount. If the 
preci})itate rapidly turns white, or if a white precipitate is 
formed to the exclusion of the red, chlorin is increased in 
amount. High chlorin is indicative of hypoacid diathesis. 

Ghjcogen, etc. — The fourth drop may be tested for glycogen 
by the addition of one drop of an aqueous solution of iodin and 
potassium iodid. This nmst be left for some time, as the test 
is not obtained until the drop is dried, then, if the color is a 
feeble violet around the edge, glycogen is indicated. If the 
color is a strong brown-red, erythrodextrin, if gray or black, a 
reducing sugar is indicated. 

Acetone. — In the fifth drop dissolve a small crystal of potas- 
sium carbonate, then add a drop of Gram's reagent, when a 
marked odor of iodoform will indicate the presence of acetone. 
Should this odor be obtained, it is better to repeat this test upon 
a microscope slide, and examine carefully for the characteristic 
hexagonal cr3^stals of iodoform (Plate V, Fig. 1). 

Specific gravity may be taken with a urinometer, reading from 
underneath the surface of the liquid. If the quantity of saHva 
should be small, it may be diluted with an equal volume of water, 
and then the last two figures multiplied by two will give the 
gravity of the undiluted sample. 

The reaction may be taken by placing a drop on litmus- 
paper. Appearance and color are noted in the sample when 
perfectly fresh; then, if a small vial is nearly filled, tightly 
corked, and set aside for twenty-four to forty-eight hours, the 
tints previously referred to may appear. The color may be a 
yellowish, greenish, or brown, according to the variety of the 
derivative of biliverdin from which the color is obtained. The 
general appearance may also change independently of any color. 
A saliva, which was when fresh hypoacid in character, is, after 48 
hours, usually markedly opalescent' and of offensive odor, while 
a hyperacid saliva may have become clear or cloudy but with- 
out odor. 



212 



DIGESTION. 



Total Solids may be obtained by evaporating over a water- 
bath 10 c.c. of thoroughly mixed sample and weighing the 
residue. If this is done in a platinum dish the residue may be 
ignited till a white ash is obtained and again weighed, and the 
result will represent the entire mineral constituents in the saliva, 
except traces of CO2 and of chlorids which may have been lost 
during ignition. If a portion of the saHva is carefully filtered, 
the epithelium cells, leucocytes, etc., will be separated. Then, 
if the total sohds in the filtrate are determined, the difference 
will be the weight of the epithelium, etc. 

Crystals from the Dialyzed Saliva. 

To obtain characteristic crystals, as has been explained in 
considering the subject of micro-chemistry, uniformity as to 
conditions under which the crystallization takes place is a 
necessity. In the case of saliva, however, we are not produc- 
ing new compounds, but simply searching for compounds already 
formed and existing in unknown proportions in the samples 
tested. It is therefore necessary to make several preparations 
of each sample, in order that we may obtain the widest range 
of possibility for characteristic crystallizations. The following 

method of procedure will usually give 
satisfactory results: For a dialyzer 
use a fairly wide glass tube, over one 
end of which has been tightly tied a 
piece of parchment (Fig. 15), or 
better, a small dialyzing tube made 
entirely of parchment. Place about 
15 c.c. of sahva in the dialyzing tube, 
and suspend it in a small beaker 
or wine-glass which contains an equal 
volume of distilled water. At the 

end of twenty-four hours the dis- 
FiG. 15. .„ , .,, . 1 ,. 

tilled water will contain the dia- 

lyzable salts in nearly the same concentration which existed 




ANALYSIS OF SALIVA. 213 

in the original saliva. Take four previously prepared cell-slides 
(niicroscojje slides on which a ring of Bell's, or other microscop- 
ical cement, has been placed), fill each cell full of the dialyzed 
saliva. Put number 1 in a warm i)lace that it may evaporate 
rapidly, leave number 2 exposed to the air at the room tem- 
perature, it will dry in half to three-([uarters of an hour. 
Place number 3 under a large beaker, or small bell-jar, and 
cover number 4 with a cover-glass, and from time to time 
examine the crystals that may be formed. Numbers 3 and 4 
will probably take several hours, perhaps several days, before 
crystallization is complete. When the crystals have appeared, 
the preparation may be preserved by mounting in xylol balsam. 
In attempting to obtain crystals from the saliva before dialyza- 
tion, results are usually unsatisfactory, owing to the presence 
of mucin and other organic substances which interfere with the 
crystalHzation. The crystals obtained by this method are 
principally sodium oxalate, lactates, and lacto-phosphate of 
lime and magnesia, and rarely urates of the alkalis. (For 
forms of these crystals see Plate VIII, Figs. 3 and 4, and Plate 
in. Fig. 3.) 

Mucin may be separated after taking the gravity by the 
addition of a little acetic acid. It should then be filtered off, 
but it will be necessary to dilute and agitate, in order that a 
fairly clear filtrate may be obtained. 

Albumin may be demonstrated in the filtrate, from which 
mucin has been separated by underlying with strong nitric 
acid. This is Heller's test for albumin in the urine, and is best 
performed in a small wine-glass with round bottom and plain 
sides. 

Ptyalin. — The presence of ptyalin may be demonstrated, and 
the conditions influencing its amylolytic action studied, by the 
two following experiments. 

Exp. 129. Action of Saliva upon Starch. — Take some filtered 
saliva in a test-tube, and place in the water-bath at 40° C. for 
five or ten minutes. Put some starch paste into a second test- 



214 DIGESTION. 

tube, and place this also in the water-bath for a while, then 
mix the two (10 c.c. of starch paste to 3 c.c. of undiluted saliva), 
and return to the water-bath. The starch is changed first to 
soluble starch (if originally a thick paste, it becomes fluid and 
loses its opalescence), then to erythrodextrin, which gives a 
red color with iodin, and finally to achroo-dextrin, which gives 
no reaction with iodin, and to maltose. Prove these changes 
as follows: Every minute or two take out a drop of the mix- 
ture, place it on a porcelain plate, and add a drop of iodin 
solution. This gives first a blue color, showing the presence 
of starch; later a violet color, due to the mixture of the blue 
of the starch reaction with the red caused by the dextrin; next 
a reddish-brown, due to erythrodextrin alone (starch being 
absent), and finally no reaction at all with iodin, proving the 
absence of starch and erythrodextrin. The fluid now contains 
achroo-dextrin and maltose. Test for the latter with Fehling's 
solution and with Barfoed's reagent. 

Exp. 130. Influence of Conditions on Ptyalin and its Amylo- 
lytic action. — Report and explain the results of the following 
experiments : 

(a) Boil a few cubic centimeters of the saliva, then add 
some starch paste, and place in the water-bath at 40° C. After 
five minutes test for sugar. 

(6) Take two test-tubes: put some starch paste in one, and 
saliva in the other, and cool them to 0° C. in a freezing mixture. 
Mix the two solutions, and keep the mixture surrounded by 
ice for several minutes, then test a portion for sugar. Now 
place the remainder in the water-bath at 40° C, and after a 
time test for sugar. 

(c) Carefully neutralize 20 c.c. of saHva with very dilute 
HCl (the 0.2% diluted), and dilute the whole to 100 c.c. Test 
the action of this neutralized saliva on starch. 

{d) To 5 c.c. of starch paste add 10 c.c. of 0.2% HCl and 
5 c.c. of neutral saUva, and expose the mixture for a while at 
40° C, and test for sugar. 



ANALYSIS OF SALIVA. 215 

(e) To 5 c.c. of starch paste add 10 c.c. of a 0.5% solution 
of Na2C03 and 5 c.c. of neutral saliva, and expose the mixture 
for a while at 40° C, and test for sugar. 

(/) Carefully neutralize (d) and (e) , and again test the action 
of the two on starch. 

(g) Mix a little uncooked starch with saliva, expose to a 
temperature of 40° C. for a while, and test for sugar. 

Exp. 131. In three separate test-tubes place a few cubic 
centimeters of dilute solutions of KCyS, of meconic acid, and 
of acetic acid; add to each a few drops of ferric chlorid, and 
notice that a sijnilar color is obtained in each case. Divide 
the contents of each tube into two portions, and to one set add 
HCl, to the other add mercuric-chlorid solution. Formulate a 
method of distinguishing from the sulphocyanates, meconates, 
and acetates. 

Tests for Abnormal Constituents. 

Acetone, glycogen, and dextrin have already been con- 
sidered. Urea may be demonstrated as follows: To a given 
volume of saliva add twice as much alcohol, this serves to 
precipitate proteids. Filter and evaporate on a water-bath 
till original volume is reached, or evaporate to less than origi- 
nal volume, and make up with distilled water. Then determine 
urea with Squibb's apparatus, as used for urine, except that 
in this case it will be necessary to replace the 2-c.c. pipette 
with a small burette, and introduce 10 c.c. of the prepared 
saliva. Then it will be necessary to allow for these 10 c.c. by 
subtracting this amount from the volume of water received in 
the graduated cylinder, and the remaining number of cubic 
centimeters, multiplied by two, will correspond to the urea in 
20 c.c. of the sample. The percentage shown on the card, 
divided by ten, will give the per cent, of urea required. 

Lactic, butyric, and acetic acids may each be tested for quali- 
tatively by the methods given under gastric digestion (q. v.). 



216 DIGESTION. 

Mercury.— A very delicate test may be made for this metal 
as follows : Collect as large a sample of saliva as possible, dilute 
with an equal volume of water, acidify with a few drops of 
HCl, throw in a few very small pieces of copper-turnings, which 
have been recently cleaned in dilute HNO3, and boil for at 
least one-half hour, keeping up the volume by occasional addi- 
tions of water. Remove the copper-filings, dry thoroughly on 
filter-paper, and place in a large-sized watch-glass (3 inches). 
In another watch-glass of similar size place one drop of solu- 
tion of gold chlorid, and quickly invert so that the drop remains 
hanging on the under side of the glass. Now place this watch- 
glass directly over the one containing the copper, so that the 
chlorid of gold shall be suspended directly above the turnings 
and perhaps a half inch from them, then gently heat the lower 
watch-glass with a very small flame, when the slightest trace 
of mercury, which may have been deposited upon the copper, 
will be volatilized, reducing the chlorid of gold, and causing a 
purpHsh ring to appear around the edge of the drop. If no 
reduction of the gold occurs, mercury is absent. 

Lead, which occasionally occurs in saliva, may be detected 
by the methods given under urine. 

Microccopical examination of the sediment should be made 
in every instance. Normal saliva will contain epithehum from 
various parts of the oral cavity, an occasional leucocyte, and 
occasional mold fungi, leptothrix, etc. Constituents, which 
perhaps are not properly classed as normal and at the same 
time are not pathological, are fat globules, a rare blood-cor- 
puscle, sarcinse, extraneous material as food particles, starch 
granules, muscle fibres, etc. An excessive amount of blood, of 
fat, pus, or micro-organisms would, of course, indicate patho- 
genic conditions. The bacteriological investigation of samples 
of saliva is always of interest, and may be necessary, but the 
detailed methods of such investigation do not lie within the 
scope of this work. 



GASTRIC DIGESTION. 217 



SECTION III.— GASTRIC DIGESTION. 

Digestion begins with the action of the saUva upon the 
carbohydrates, and if mastication is sufficiently prolonged, the 
ptyalin may convert an appreciable quantity of starchy food 
into a more soluble form before it reaches the stomach. In the 
stomach the amylolitic action of the saliva is stopped by the 
contact with the gastric juice. A certain amount, however, of 
salivary digestion takes place within the stomach, due to the 
fact that considerable time necessarily elapses before the acid 
of the gastric juice has been secreted in sufficient quantity to 
completely permeate and acidify the mass of food received 
from the oesophagus. As has been previously shown, a very 
feeble degree of acidity is conducive to the activity of the 
amylolytic ferment. The average alkalinity of the saliva, cal- 
culated as Na2C03, is about 0.15 of 1%. 

The first step in the gastric digestion is probably the union 
of the stomach HCl with the proteids, forming acid albumins 
or allied bodies which are changed by pepsin, which is the 
active digestive ferment of the stomach, into the albumoses, 
and slight amounts of the various peptones, following practi- 
cally the changes produced experimentally on page 219. 

Pepsin is an active proteolytic enzyme occurring in the cells 
of the stomach-wall as pepsinogen, which is decomposed by 
the HCl with the formation of free pepsin. Pepsin works only 
in faintly acid solutions, and in the stomach carries the diges- 
tion of proteids but Httle beyond the stage of the proteoses. 

Hydrochloric acid, obtained from the fundus glands by an 
interchange of radicles between alkahne chlorids and the car- 
bonates of the blood.* The quantity present varies from to 
^/lo per cent, 0.18% being about the most favorable for peptic 
activity. Aside from HCl, various organic acids may be pres- 
ent in the stomach contents; lactic acid, butyric acid, and acetic- 

* Long's Physiological Chemistry. 



218 DIGESTION. 

acid are the most important of this class, tests for which are 
referred to under analysis of gastric contents. 

Rennin is a second enzyme found in the stomach. This, like 
pepsin, also exists as a zymogen, and is liberated or developed 
by the presence of acid. Its action is peculiarly the curdling 
of milk, i.e., the decomposition of caseinogen (Exp. 137), and 
consequent coagulation of the casein. A third enzyme, existing 
in the stomach in very small quantities, is a gastric lipase, or 
stomach steapsin, a fat-splitting enzyme, the action of which 
is comparatively weak, and of but slight importance. 

Analysis of Gastric Contents and Experiments with 

Pepsin. 

The following solutions will be found in the laboratory: 

A. A .2% Solution of HCl. — This is prepared by diluting 
6.5 c.c. of concentrated HCl (sp. gr. 1.19) with distilled water 
to 1 liter. 

B. A Solution of Pepsin. — Prepared by dissolving two grams 
of pepsin in 1000 c.c. of water. 

C. A Pepsin-hydrochloric-acid Solution. — Prepared by dis- 
solving two grams of pepsin in 1000 c.c. of solution A. 

Or, add to 150 c.c. of solution A about 10 c.c. of the glyc- 
erine extract of the mucous membrane of the stomach. 

Exp. 132. Take five test-tubes and label a, h, c, d, e. Fill 
as indicated below. Place in a water-bath at 40° C, and 
examine an hour later, and again the next day. 

(a) 3 c.c. pepsin solution + 10 c.c. water + a few shreds of 
fibrin. 

(6) 10 c.c. 0.2% HCl + a few shreds of fibrin. 

(c) 3 c.c. pepsin solution + 10 c.c. 0.2% HCl, and a few 
shreds of fibrin. 

{d) 3 c.c. pepsin solution + 10 c.c. 0.2% HCl, boil, and then 
add a few shreds of fibrin. 

(e) 3 c.c. pepsin solution + 10 c.c. 0.2% HCl, and a few 



GASTRIC DIGESTION. 219 

shreds of fibrin which have been tied firmly together into a 
ball with a thread. 

Make a note of all changes. 

Exp. 133. Filter c. Neutralize with dilute NasCOs. Filter 
again. Why? Test the filtrate for the biuret reaction. 

Exp. 134. To 5 grams fibrin add 30 c.c. of the pepsin solution 
and 100 c.c. 0.2% HCl. Set in the water-bath at 40° C, stirring 
frequently, and leave in the water-bath overnight. Observe 
the undigested residue, on the following day, and also a slight 
flocculent precipitate. What is this precipitate? 

Filter and carefully neutraUze the filtrate. A precipitate 
varying with the progress of the digestion will form. AVhat 
is it? 

Remove this by filtration, and saturate this filtrate with 
(NH4)2S04. Filter. Save precipitate and filtrate. Of what 
does each consist? 

Exp. 135. Dissolve the last precipitate of Exp. 134 in water, 
and try the following tests: 

(a) Biuret reaction. 

(6) Effect of boiling. 

(c) Test with HNO3, as in performing test for albumin in the 
urine. 

Exp. 136. To the last filtrate of Exp. 134 add an equal vol- 
ume of 95% alcohol, and stir thoroughly. The peptones will 
collect in a gummy mass about the stirring-rod. 

(a) Determine the solubility of peptones in water. 

(6) What is the effect of heat when so dissolved? 

(c) Try the biuret reaction. 

Exp. 137. Demonstration of the Rennet Enzyme. — Place 10 c.c. 
milk in each of three test-tubes. Label the test-tubes 1, 2, 3. 

To 1 add a drop of neutralized glycerine extract of the 
mucous membrane of the stomach (made from the stomach of 
the calf). 

To 2 add a drop of a neutralized glycerine extract, and boil 
at once. 



220 DIGESTION. 

To 3 add a few cubic centimeters of (NH4)2C204 solution, 
and then a drop of a glycerine extract. 

Place these tubes in the water-bath at 40° C, and examine 
after five to ten minutes. Explain results in each case. 

Continue heating tube 3 for half an hour, then add 2 or 3 
drops CaCl2 solution. The liquid instantly solidifies. Why? 

Exp. 138. Digestion of Casein. — Determine the products of 
the digestion of the curd from the last experiment. 

Exp. 139. Tests for Free Hydrochloric Acid. — Try each of the 
following tests with (a) HCl (0.2%, 0.05%, and 0.01% succes- 
sively); (b) lactic acid (1%); (c) mixtures containing equal 
volumes of (a) and (h). Tabulate the results. 

(a) Dimethylamidoazohenzol. — Use one or two drops of a 
0.5% alcoholic solution. In the presence of free mineral acids 
a carmine-red color is obtained. 

(5) Gunzhurg's Reagent. — Phloroglucin, 2 grams; vanillin, 
1 gram; alcohol, 100 c.c. Place two or three drops of the solu- 
tion to be tested in a porcelain dish, add one or two drops of 
the reagent, and evaporate on a water-bath. In the presence 
of free hydrochloric acid a rose-red color develops. 

(c) Boas' Reagent. — This is prepared by dissolving 5 grams 
of resublimed resorcin and a gram of cane-sugar in 100 grams 
of 94% alcohol. Take three or four drops each of the reagent 
and the solution to be tested, and cautiously evaporate to 
dryness. In the presence of a free mineral acid a rose or Ver- 
million red color is obtained. This gradually fades on coohng. 

{d) Tropceolin 00. — Use one or two drops of a saturated 
alcoholic solution. 

(e) Congo-red. — Use filter-paper, which has been dipped into 
a solution of the reagent, and then dried. 

Exp. 140. To 5 c.c. egg-albumin in solution add 1 c.c. of 
0.2% HCl. Mix thoroughly, and test for the presence of free 
HCl. \ATiat is the result? How do you explain it? Repeat 
the test, using a solution of pepton in place of the egg-albumin. 

Exp. 141. Tests for Lactic Acid. — Uffelmann's reagent. Mix 



GASTRIC DIGESTION. 221 

10 c.c. of a 4% solution of carbolic acid with 20 c.c. of water, 
and add a drop or two of ferric chlorid. 

To 5 c.c. of the reagent add a few drops of the lactic-acid 
solution. Note the canary-yellow color. 

Does the presence of free IICl interfere with this reaction? 

A more delicate reagent is obtained by adding three or four 
drops of a 10% ferric-chlorid solution to 50 c.c. of water. Such 
a solution has a very faint yellow color, which is distinctly 
intensified by lactic acid. 

Using 5 c.c. of this near y colorless solution for each experi- 
ment, note the effect of (a) 2% HCl; (6) acid phosphate of 
sodium; (c) alcohol; {d) glucose; (e) cane-sugar. What con- 
clusions do you reach concerning the value of this list, when 
applied directly to the gastric contents? 

The test is best applied to an aqueous solution of the ethereal 
extract of the gastric contents. Add to the contents two drops 
of HCl, boil to a syrup, and extract with ether. Dissolve the 
residue obtained upon evaporation of the ether in a little water, 
and test for lactic acid. 

Exp. 142. Test for butyric acid; see ethyl butyrate, page 138. 

Exp. 143. Test for acetic acid; see acetates (page 49). 

Exp. 144. The acidity of the gastric contents may be deter- 
mined as follows : To 5 c.c. of the filtered contents, diluted with 
25 to 30 c.c. of water in an Erlenmyer flask, add 2 or 3 drops of 
a solution of dimethylamidoazobenzene. Titrate with N/10 
alkali till the color changes to a yellow which fairly matches 
the indicator, this represents the free HCl. To this mixture 
add a few drops of phenolphthalein solution, and continue the 
titration until a permanent pink color is obtained. The N/10 
a'kaU used will represent the total acidity, combined HCl and 
organic acids. The organic acids w^ill not be present in gastric 
contents in the presence of any appreciable amount of free 
HCl, as they are derived entirely from fermentations which are 
inhibited by the hydrochloric acid. 



222 DIGESTION. 



SECTION IV.— PANCREATIC DIGESTION AND BILE. 

It may be an aid, in remembering the various digestive fer- 
ments, to note that in the saUva we have one principal ferment 
ptyahn, in the stomach we have two principal ferments, pepsin 
and rennin, in the pancreatic juice, three active ferments. First, 
a proteolytic enzyme, known as trypsin, which continues the 
work of the gastric juice, and converts the proteoses into pep- 
tones, tyrosin, leucin, etc. The pancreatic juice is a much more 
energetic digestive agent than the gastric juice, but differs in 
that it is an alkali secretion, and neutralizes any acid which 
may have been obtained from the stomach. Next, the amylo- 
lytic enzyme known as amylopsin. Here, again, we have an 
•enzyme much more energetic in its action upon carbohydrates 
than the ptyalin of the saliva. It converts starch into maltose 
and to some extent to dextrin. The amylopsin is active in 
faintly alkaline or very faintly acid solution; more acid, how- 
ever, retards its action. 

Steapsin is the fat-splitting enzyme of the pancreatic juice. 
It splits the fat, as indicated on page 140, into glycerine and 
fatty acids, and also acts as an emulsifying agent. The free 
fatty acids thus formed unite with the alkaline bases found in 
the intestines to form soaps, which are also active emulsifying 
agents. 

Bile. — A secretion produced by the liver and stored in the 
gall-bladder, from which it is delivered to the intestines, where 
it aids materially in emulsification and absorption of the fats. 

Composition of Bile. — Its composition is very complex, 
but there are two acids and two coloring matters which are of 
particular importance, and derivatives of which indicate the 
presence of bile in saliva, urine, blood, etc. The acids are 
taurocholic and glycocholic, existing principally as sodium or 
potassium salts. The coloring matters are bilirubin and bili- 
verdin; the former predominates in human bile and the latter 



PANCREATIC DIGESTION AND BILE. 223 

in OX bile. Glycocholic acid upon hydrolysis splits into a 
simpler acid (cholalic) and glycocoU, glycocoll being an amido- 
acetic acid (page 148), which is undoubtedly an antecedent of 
urea. Both of the bile-pigments are derived from the coloring 
matter of the blood. The appearance of either of these or of 
their derivatives, in either urine or saliva, is indicative of patho- 
logic conditions either of the liver- or bile-ducts, causing ob- 
struction to the outflow of the bile or a destruction of the red- 
blood corpuscles.* The blood pigments, according to Michaels, 
are easily demonstrable in the desiccated saliva by means of 
polarized light. 

Experiments with Pancreatic Juice. 

Exp. 145. Proteolytic Action. — To 25 c.c. of a 1% solution of 
Na2C03 add a few drops of the pancreatic extract. Place 
some pieces of fibrin in this liquid, and keep in the water-bath 
at 40° C. till the fibrin has disappeared (one to two hours prob- 
ably). Observe the digestion from time to time. Note that 
the fibrin does not swell and dissolve as in gastric digestion, but 
that it is eaten away from the edges. 

Filter.- What is the precipitate? Carefully neutralize the 
filtrate with 0.2% HCl. Another precipitate may appear. 
What is this? 

Again filter, if necessary, and test the filtrate for proteoses 
and peptones as directed under gastric digestion. 

Exp. 146. Formation of Leucin and Tyrosin. — Perform a 
similar experiment, using boiled fibrin and adding a few drops 
of a 20% solution of thymol, or a few drops of chloroform 
water. Why use boiled fibrin, and why add thymol or chloro- 
form ? Digest for forty-eight hours, and then examine as follows : 
Filter, neutralize, and concentrate by evaporation on the 
water-bath. Crystals of tyrosin (and possibly leucin) usually 
separate. Examine microscopically. 

* Ogden. 



224 DIGESTION. 

Exp. 147. Amylolytic Aclion. — To some starch paste in a 
test-tube add a drop or two or the pancreatic extract and place 
in the water-bath at 40° C. After a few minutes test for 
sugar and report the result. 

Exp. 148. The Piolytic {Fat-splitting) Action. — For the 
demonstration of this action use natural pancreatic juice, or 
finely divided fresh pancreas, or a recently prepared extract. 

To some perfectly neutral olive-oil, colored faintly blue- 
with litmus, add half its volume of the pancreatic extract,, 
shake thoroughly, and keep at 40° C. for tw^enty minutes. 
Record the result. Reserve for next experiment. 

Exp. 149. Emulsifying Action. — To 10 c.c. of a 0.2% solu^ 
tion of Na2C03 add a few drops of the mixture used in Exp. 148. 
Shake thoroughly, and report the result. Referring to the 
earlier experiments on emulsification (see Fats), explain the 
efficacy of the pancreatic juice in emulsifying fats. 

Experiments with Bile. 

Exp. 150. Color. — Note the difference in color between human 
bile and ox bile. Explain. 

Exp. 151. Reaction. — Dilute some bile with four parts of 
water. Immerse a strip of red litmus-paper, then remove and 
wash with water. Note the recation. 

Exp, 152. Nucleo-alhumin. — Dilute bile with twice its volume 
of water, filter if necessary, and add acetic acid. What is the 
precipitate? How distinguished from mucin? 

Exp. 153. Filter (152) and test the filtrate for proteids.. 
Report the result. 

Exp. 154. Separation of Bile Salts- — Mix 20 c.c. of bile with 
animal charcoal to form a thick paste, and evaporate on the 
water-bath to complete dryness. Pulverize the residue in a 
mortar, transfer to a flask, add 25 c.c. of absolute alcohol, 
and heat on the water-bath for half an hour. Filter. To the 
filtrate add ether till a permanent precipitate forms Let the 



PANCREATIC DIGESTION AND BILE. 225 

mixture stand for a clay or two, and then filter off the crystalline 
deposit of bile salts. Save the filtrate which contains choles- 
terin. (Plate VI, Fig. 6.) 

Exp. 155. Bile-pigments. — (a) Gmelin's Test. — Take some 
bile in a wine-glass and underlie with yellow HNO3, in the manner 
described in testing saliva for albumin. Notice the play of 
colors, beginning with green and passing through blue, violet, 
and red to yellow, at the junction of the two liquids. Ex- 
plain. 

(6) lodin Test. — Place 10 c.c. of dilute bile in a test-tube, 
and add slowly two or three cubic centimeters of dilute tincture 
of iodin, so that it forms an upper layer. A bright green ring 
forms at the line of contact. 

Exp. 156. Cholesierin. — Examine under the microscope the 
cyrstals obtained by the cautious evaporation of the alcohol- 
ether filtrate of Exp. 154. For color reactions refer to demon- 
strations. 

Exp. 157. Action of Bile in Digestion. — (a) Take three test- 
tubes. In one mix 10 c.c. of bile and 2 c.c. of neutral olive-oil; 
in the second, 10 c.c. of bile and 2 c.c. of rancid olive-oil; in 
the third, 10 c.c. of water and 2 c.c. of neutral oil. Shake 
and place in a w^ater-bath at 40° C. for some time. Note the 
extent and the permanency of the emulsion in each case. 

(6) Into each of two funnels fit a filter-paper. Moisten one 
with water and the other with bile, and into each pour an 
equal volume of olive-oil. Set aside for twelve hours (w^ith a 
beaker under each funnel). Do you notice any difference in 
the rate of filtration? 

(c) Add drop by drop a solution of bile salts to (a) a solution 
of egg-albumin; (b) a solution of acid-albumin; (c) a solution 
obtained by digesting a bit of fibrin in gastric juice and filter- 
ing. Explain the results. 



PART VIII. 

URINE. 



SECTION I— PHYSICAL PROPERTIES OF URINE. 

Urine is a solution of waste products from the blood. It 
contains, normally, certain coloring matter, urea, uric acid, in 
combination with alkahne bases, various organic constituents 
in very slight amounts, including, perhaps, albumin and sugar, 
chlorid of sodium, sulphates and phosphates of the alkalis and 
' the alkaline earths. Abnormally the urine may contain albumin, 
sugar, uric acid as such, bile, salts of the heavy metals, lead, 
mercury, and arsenic; occasionally albumose, peptones, lac- 
tates, lacto-phosphates, oxalates, carbonates, hippuric acid, 
also organic compounds, resulting from insufficient or imper- 
fect oxidations, as amido-acids, leucin, tyrosin, and acetone 
bodies. 

We are to study the urine, not primarily with a view to the 
diagnosis of renal disease, which is more particularly the prov- 
ince of the physician, but to detect irregularities or deficiencies 
in the body metabolism, and, as far as possible, we are to study 
the methods whereby we may correct and regulate the mal- 
nutrition which lies at the foundation of many diseases of the 
oral cavity. As has been previously stated by the author,* 
if there are diseases of the oral cavity which may have their 

* International Dental Journal, January, 1905. 

226 

r 



PHYSICAL PROPERTIES OF URINE. 227 

etiology in some systemic derangement not easily apparent, 
and if such diseases are to receive the attention of the dentist, 
he should obtain all possible light on his case, and at present 
a quantitative analysis of the urine is of greater value than 
any other laboratory aid. In examining a sample of urine to 
obtain information as above indicated, it is essential that the 
sample be a portion of the mixed twenty-four-hour cjuantity, 
and that the total amount of the twenty-four-hour excretion 
be known. In collecting samples for such analysis a conven- 
ient method is to give the patient a one- or two-dram vial, nearly 
filled with water, and containing three or four drops of a com- 
mercial formaldehyde solution, with instructions to empty this 
into the bottle or other receptacle, in which the twenty-four- 
hour sample is collected. Formaldehyde if used in this amount 
has no effect on the subsequent analysis and is a sufficient pre- 
servative. 

Physical Properties. 

Quantity. — The quantity of urine passed in twenty-four 
hours normally is about 1200 to 1400 c.c. for an adult female 
and 100 or 200 c.c. more than this for the male. The amount 
is increased in Bright's disease, in diabetes, and various other 
pathological conditions, also in cold weather when less mois- 
ture is given off from the skin. Normally the quantity passed 
during twelve day hours, as 8 a.m. to 8 p.m., will exceed the 
amount overnight from 8 p.m. to 8 a.m. In cases of chronic 
interstitial nephritis the twelve-hour night quantity exceeds the 
day, hence it is desirable in collecting a twenty-four-hour sam- 
ple to divide the time as suggested, and measure the amounts 
separately, especially if there is any suspicion of any chronic 
kidney disease. A diminished quantity of urine may indicate 
simply a diminished amount of water taken into the system. 
The urine is diminished pathologically in acute conditions, such 
as fevers, etc., but such samples rarely reach the dental prac- 
titioner. 



228 URINE. 

Color. — The normal color of the urine is usually given as 
straw color or pale yellow. If lighter than this the color is 
regarded as pale, if darker than normal it is regarded as high. 
The urine may also be colored by various abnormal constitu- 
ents; it may be bright red from the presence of blood, or 
chocolate colored with a so-called coffee-ground sediment from 
decomposed-blood coloring matter. It may be brown to yel- 
low, bright blue or green, due to the ingestion of various drugs. 
If bile is present in any quantity in the urine it will have a 
dark or smoky appearance, and, upon shaking, the foam will 
have a distinctly yellowish or yellowish-green tint. 

Appearance. — Aside from these variously colored samples 
urine may sometimes have a smoky appearance, due to the 
presence of hematoporphyrin or iron-free hematin, often found 
in cases of lead-poisoning. It may have a milky appearance,, 
due to presence of finely divided fat globules, as in chylous 
urine, due to parasitic disease of the blood. It may be cloudy 
from four principal causes: first, amorphous urates; second^ 
amorphous phosphates; third, pus; and fourth, bacteria; 
these may easily be distinguished. The application of a slight 
degree of heat (insufficient to cause coagulation of albumin) 
will redissolve the urates, and clear a urine which is cloudy 
from this cause. A deposit of phosphates is increased by the 
application of heat, but clears easily upon the addition of a 
few drops of acetic acid. A urine cloudy from the presence 
of pus is not cleared by either of these methods, but the cloud 
settles with comparative rapidity and pus corpuscles are easily 
recognized by microscopical examination of the sediment. If 
bacteria are present in sufficient quantity to cause cloudiness, 
the sample is apt to be alkaline in reaction and will not clear 
upon filtering. If it is necessary to obtain a clear solution, a 
little magnesium mixture may be added to the urine, then a 
little sodium phosphate; warm gently with agitation, when 
the precipitated ammonium magnesium phosphate will me- 
chanically carry down the bacteria, and a filtrate may be ob- 



PHYSICAL PROPERTIES OF URINE. 



229 




tained which, after acidifying with dilute acetic acid, will be 
suitable for an albumin test. 

Specific Gravity. — The gravity is most conveniently taken 
with a urinometer (Fig. 16). Care should be taken in the 
selection of this instrument that the scale graduation is accu- 
rate. The fact that the instrument will sink in distilled water 
at the proper temperature (usually 60° F., loj^ C.) to the mark, 
is not a sufficient proof of its accuracy, as many cheap instru- 
ments will do this, and give erroneous readings 

at the higher markings of the scale. Distilled ^ -? 

water is represented by 1000, and the relative \ 
increase in the comparative gravity of urines 
will be easily represented on the scale ranging 
from 1000 to 1050. As the first two figures of 
the specific gravity are always the same (10), 
they are usually omitted from the scale which 
is made to read from to 50 or 60. The 
reading should be made, if possible, from under- 
neath the surface of the liquid, as the Hquid is 
usually drawn around the stem by adhesion, 
so that accurate readings from the surface are difficult. The 
specific gravity of normal urine is from 1018 to 1022, it de- 
creases in cases where the quantity is much above the normal 
(polyurias), unless sugar is present. It is increased by the 
presence of sugar or by concentration, whereby the normal 
solids are relatively increased. In case the quantity of urine 
is too small for the determination of the gravity in the usual 
way, the urinopyknometer, devised and recommended by 
Dr. Saxe in his ^' Examination of the Urine," may be em- 
ployed. 

Reaction. — The reaction of urine is normally acid to litmus- 
paper, due to the presence of acid sodium phosphate. The 
degree of acidity is roughly indicated by the intensity of color 
produced with the carefully prepared litmus-paper. More 
accurate results may be obtained by a regular volumetric 



Fig. 16. 



230 - URINE. 

examination, or by the test for urinary acidities given by Freund 
and Topfer who suggest the f ohowing method : 

^'To 10 c.c. of the urine add two to four drops of a 1% 
solution of ahzarin. If the resulting color is pure yellow, 
free acids are present; if deep violet, combined acid salts. If 
none of these colors appear, there are present acid salts of 
the type of disodic phosphate. The amount of one tenth 
normal HCl standard solution required to produce a pure yellow 
color represents the alkaline salts, while the amount of one 
tenth normal sodium hydrate required to cause a deep violet 
represents the acid salts." 



SECTION II.— NORMAL CONSTITUENTS. 

The more important normal constituents of the urine are 
urea, uric acid (combined as urates), chlorids, phosphates, 
sulphates, coloring matters (urophain and indoxyl); traces of 
mucin, organic acids, carbonates, hippuric acid, creatin, and 
creatinin may also be present. The total normal solids are 
composed approximately of 50% urea, 25% chlorid of sodium; 
at least one half of the remainder are phosphates and sul- 
phates. We see that the constituent which most influences the 
specific gravity is the urea, and in normal samples the specific 
gravity is an index of the amount of urea present. The total 
solids may be calculated by multiplying the last two figures 
of the specific gravity by. 2 J,* which will give the number of 
grams of soHds in one Hter of urine — from this the solids in the 
twenty-four-hour amount may be easily calculated. 

Urea. 

The chemistry of urea has been already considered (page 
153). 

Detection. — A qualitative test for this substance is obvi- 

* Coefficient of Haeser. 



NORMAL CONSTITUENTS. 



231 



ously superfluous, although such may be made by obtaining 
the crystals of urea nitrate or oxalate (page 155). The quan- 
tity of urea is of great importance, especially in cases where 
there is any question in regard to the body metabolism or the 
amount of nitrogen excreted. By far the greater proportion 
of all nitrogenous waste is eUminated by the kidneys in the 
form of urea, a comparatively slight amount as other nitrog- 
enous constituents of the urine, a still smaller amount in 
the faeces, and traces only by other avenues. The urea may 
be quantitatively determined by various methods, the hypo- 
bromite method is the most practical. 

Quantitative Determination. — There are various forms of 
apparatus used in connection with this process, but the one 




Fig. 17. 

devised by Dr. Squibb will probably give the most accurate 
results with the least practice. The use of this apparatus may 
be best explained by reference to the above cut. 

The first step in the use of this apparatus is to completely 
fill the bottle A, including the tubes D and H, with water, 
with the glass plug E closing the lower end of D. Next put 
5 c.c. each of a 40% solution of caustic soda and a bromine 
solution in potassium bromide* into B. Place the stopper 
in B and connect the tube C at H, then fill accurately the 
2-c.c. pipette with urine. Place in position in the stopper of 

* For preparation of this solution see appendix. 



232 



URINE. 



B as shown in the cut, remove E from the rubber tube D, and 
allow D to fall to the bottom of the graduate as indicated. 
Pressure is now applied to the bulb of the pipette, so that the 
2 c.c. of urine is forced with moderate rapidity into the bottle. 
As the pressure on the bulb is released, water will be drawn 
back into A, and it is essential that the end oiD is underwater 
during this portion of the process. Bottle B should be agitated 
to insure complete decomposition of the urea. Nitrogen and 
carbon dioxid are at once evolved according to the reaction 
on page 154. The 40% solution of caustic 
soda is strong enough to absorb and hold 
the CO2. The nitrogen passes into A, 
forcing a corresponding volume of water 
into the graduate. This volume of gas, 
read in cubic centimeters of the water, 
will give the percentage of urea in the 
sample examined, 1 c.c of nitrogen being 
equivalent to 0.126 of urea. 

Doremus' apparatus is shown in Fig. 
18. One cubic centimeter of the urine is 
used instead of i:wo, and the whole appa- 
ratus is filled with the hypobromite solu- 
tion. This apparatus is simpler than Squibb's, but requires 
greater care in manipulation in order to obtain equally accu- 
rate results. 




Fig. 18. 



Uric Acid. 

Uric acid and its antecedents, the xanthin bases, are derived 
from the decomposition of nuclein and nucleoproteid. For 
chemistry of this substance, see pages 156 and 158. The uric 
acid is increased by a highly nitrogenous diet and certain 
vegetable substances which contain purin (page 157) derivatives, 
such as coffee, tea, and cocoa. The red meats, so-called, beef, 
mutton, etc., are regarded as the most abundant source of uric 
acid and urates. As previously suggested uric acid does not 



NORMAL CONSTITUENTS. 233 

occur in normal urine as such, but is combined with the alka- 
line bases. 

Detection. — It is unnecessary to make a qualitative test in 
urine, as urates are always present. If a qualitative test is de- 
sired the murexid test, as given on page 160, is available. Uric 
acid is best determined quantitatively by the centrifugal method 
as devised by Professor Cook. The detail of this method is 
as follows: Measure 10 c.c. of urine into a graduated tube, used 
in the centrifugal machine, add a few grains of sodium car- 
bonate, and about 3 c.c. of strong ammonium hydrate. Place 
in the centrifuge, and allow to run for one or two minutes, 
then carefully decant the clear urine into another graduate 
tube, leaving the precipitate which consists of earthy phosphates. 
The bulk of this precipitate may be noticed and an idea obtained 
as to whether the earthy phosphates are present in normal 
quantities or not. To the clear urine add 2 or 3 c.c. of ammo- 
niacal silver-nitrate solution (AgNOs, 5 grams, distilled water, 
80 c.c, strong ammonia, 20 c.c), and run in the centrifuge till 
the precipitate of silver urate has reached its lowest obtainable 
reading. The ammonia will prevent the precipitation of 
chlorids and, unless iodids or bromids are present, the precipi- 
tate will be fairly pure silver urate, each tenth of a cubic centi- 
meter of the precipitate being equivalent to 0.001176 gram of 
uric acid in the 10 c.c of urine used, or 0.01176%. 

Chlorids. 

The chlorids are represented in the urine chiefly by sodium 
chlorid. This is present to the extent of 12 to 20 grams in 
twenty-four hours. An increase above this quantity is unusual, 
although it simply indicates an increase in the ingested salts, 
and is without clinical significance. The chlorin is diminished 
in dropsy, acute stages of pneumonia, and in fevers generally. 

Detection. — The usual qualitative test with silver nitrate and 
nitric acid is employed for detection of chlorid in the urine. 



234 URINE. 

If one drop of a strong solution of silver nitrate (1 to 8) is- 
allowed to fall into the wine-glass in which the albumin test 
has been made (q.v.), the appearance of the resulting precipi- 
tate will give a rough idea of the quantity of chlorin present.. 
If a solid ball of silver chlorid is formed which does not become 
diffused upon gently agitating the contents of the glass, the 
chlorin is normal or increased. If the precipitate falls as a 
cloud distributed throughout the liquid, the chlorin is dimin- 
ished. The chlorin may be quantitated by precipitation with 
silver nitrate in 10 c.c. of urine, and the precipitate settled in a 
centrifuge-tube to constant reading, but this method is not 
recommended, as the precipitate is a bulky one, and usually 
takes a long time for thorough settling. The titration with 
silver nitrate, using potassium chromate as an indicator, really 
takes less time, and is much more accurate. This titration is 
made in the usual way (see page 101), except that, inasmuch as 
phosphates and urates are also precipitated, from three tenths ta 
1 c.c. may be deducted from the amount of the silver-nitrate 
solution used according as it is, much or little, thus allowing 
for these substances. An accurate titration of chlorin may 
be made by acidifying the urine with nitric acid, adding an 
excess of standard silver- nitrate solution, and titrating back with 
a standardized sulphocyanate solution (preferably of the same 
strength as the AgNOs solution), using ferric sulphate for an 
indicator. But as a rule the simpler method gives results 
which for clinical purposes are equally valuable as this more 
tedious though more accurate process. 

Phosphates. 

The phosphates in the urine are of two kinds, the alkaline 
phosphates, Na2HP04 and NaH2P04, etc., and the earthy 
phosphates represented by the magnesium and the calcium 
phosphates. The phosphates are normally present to the 
extent of two and a half to three and a half grams, calculated 
as P2O5 (in twenty-four hours). 



NORMAL CONSTITUENTS. 235 

The triple phosphates, ammonium magnesium phosphates 
(Fig. 4, Plate I), are the forms in which phosphoric acid is usu- 
ally found in urinary sediment. Crystals of acid calcium 
phosphate are occasionally found, and resemble the acid sodium 
urate in form (Fig. G, Plate III), except that they are usually 
a little broader and more often occur in fan-shaped clusters. 
They may be distinguished by treatment with acetic acid, 
which dissolves the calcium phosphate promptly, while the 
urate is slowly dissolved, and crystals of uric acid appear after 
a little time. The phosphates are deposited from neutral 
or alkaline urines, and when this precipitation takes place 
within the body, the crystals cause more or less irritation to 
urinary tract, and may form aggregations which result in cal- 
culi. Phosphates are supplied by either a cereal or meat 
diet. They may be much increased in diseases accompanied 
by nervous waste, or by softening and absorption of bone. 
Phosphates are diminished in gout, in chronic diseases of the 
kidney, and during pregnancy. 

Detection. — A qualitative test for earthy phosphates (E.P.) 
may be made by taking a test-tube half-full of urine, and mak- 
ing alkaline with ammonium hydrate. AATien the precipitate has 
thoroughly settled, if it is about } to J inch in depth, it represents 
normal, earthy phosphates. If this mixture is now filtered, 
the alkaline phosphates (A.P.) may be determined in the filtrate 
by the addition to the solution of one third its volume of mag- 
nesium mixture.* The precipitate after settHng will be J to 
f of an inch in depth if normal. The total phosphates may 
be quantitated in the centrifugal machine by adding 5 c.c. 
of magnesium mixture to 10 c.c. of urine. Each tenth of a. 
cubic centimeter of the centrifugalized sediment will be equiva^ 
lent to 0.0225 of P2O5. 

* See Appendix 



236 URINE. 



Sulphates. 



The sulphates in the urine are present as alkahne sulphates, 
K2SO4 and Na2S04; also as ethereal sulphates, represented by 
such compounds as indoxyl" potassium sulphate, page 167. 

Detection and Determination. — The sulphates may be de- 
tected by precipitation with barium chlorid in HCl solution. If 
the precipitate is obtained from 10 c.c. of urine and centrifugal- 
ized to constant reading, the per cent of sulphuric acid by weight 
will be one fourth of the volume per cent of the precipitate. 
The sulphates follow rather closely the urea, and their deter- 
mination is not of great importance. They are increased in 
acute fevers, and diminished in chronic diseases generally, and 
markedly diminished in carbolic-acid poisoning. (Ogden.) 

Urophain. 

The urophain test of Heller is an easily applied test for 
coloring-matters, urobilin, and other coloring-matters. It 
has little clinical significance, because it is influenced by the 
presence of many other urinary constituents. The urophain 
is supposed to be increased in any disease in which the red 
corpuscles are being destroyed. The test is made by placing 
7 c.c. of strong sulphuric acid in a wine-glass, and allowing 
double the quantity 0^ urine to fall from a sufficient height 
to thoroughly mix the liquids, when an immediate dark-red 
color indicates a normal condition. 

Indoxyl. 

The indoxyl is of considerable importance, as an increase 
above the normal amount is indicative of increased putrefaction 
of nitrogenous substances taking place in the small intestine. 
Indoxyl may also be increased by acute inflammatory process 
of the peritoneal cavity. Ordinary constipation does not 
increase the indoxyl. The test for indoxyl depends upon the 



ABNORMAL CONSTITUENTS. 237 

oxidation of the incloxyl potassium sulphate to indigo blue 
according to the following reaction: 

2C8H6NKSO4 + 02 = 2C8H5NO + 2KHSO4. 

Indoxyl potassium sulphate. Indigo. 

Detection and Determination.— 15 c.c. of strong HCl is 
placed in a wine-glass, and a single drop of concentrated 
nitric acid added; then 30 drops of urine are stirred into the 
mixture. If indoxyl is present, an amethyst color develops 
in from five to fifteen minutes. If the color is purple, the 
indoxyl is increased. Variation of the amount of indoxyl 
within normal limits is rather a wide one, and the indoxyl 
may be reported as high or low, normal, increased or diminished. 



SECTION III.— ABNORMAL CONSTITUENTS. 

The principal abnormal constituents are albumin, sugar, 
acetone, bile, and various crystalline salts, discoverable either 
by microscopical examination of the sediment, or by evapora- 
tion of a clear fluid, and examination with the micropolariscope. 

Metallic substances, arsenic, lead, and mercury are occa- 
sionally present, and tests should be made for them when gen- 
eral symptoms or condition of the kidney indicate metallic 
poison. Albumin is probably present in minute traces in the 
majority of urines. When in sufficient quantity to be detected 
by the usual laboratory methods, it is essential that w^e learn 
the source from which it has been derived, for the simple pres- 
ence of even a considerable trace of albumin may be of but 
slight clinical importance. Albumin may indicate either a 
pathological condition of the kidney, which allows the entrance 
into the renal tubules of serum-albumin from the blood, or it may 
indicate a change in the composition of the blood, whereby the 
albumin more easily passes through the renal membranes, or its 
presence may be due to irritations from various sources of the 



238 URINE. 

urinary tract; and, as regards the bearing of albuminurias on 
dental disease, it is sufficient simply to determine whether 
renal disturbance is primary or secondary to some other trouble, 
such as heart disease, or purely local, such as may be caused 
by bacteria or crystalline elements. 

Detection.— Albumin may be detected by either of two 
simple methods. It is often desirable to use both of these 
methods, thereby eliminating possible confusion from the 
presence of substances other than albumin, which may respond 
to one of the two tests, but not to both. 

The first consists simply in underlying about 25 c.c. of 
filtered urine in a wine-glass with concentrated nitric acid. 
The wine-glass should be tipped as far as possible, and the 
acid allowed to run very slowly down the side. This method 
is preferable to the use of the apparatus known as the albu- 
minoscope or Horismascope (Fig. 19). As this latter method 





Fig. 19. Fig. 20. 

does not provide for sufficient mixing of nitric acid with the 
sample, the albumin is shown by a narrow white ring at 
the point of contact of the two liquids. A white ring above 
the point of contact is not albumin, but is composed of acid 
urates, indicating an excess of urates in the sample (Fig. 20). 
The albumin, in distinction from this band, occurs directly 
above the acid, and is usually reported as the slightest pos- 
sible trace when just discernible; as a slight trace when well 
marked, but not dense enough to be seen when looking 
through the liquid from above; as a trace, when the white 



ABNORMAL CONSTITUENTS. 



239 



liJ 



cloud may be seen by looking down into the glass from 
above, and a large trace if plainly visible in this way. 
Anything more than a trace should be quantitated in 
the centrifugal machine by mixing 10 c.c. of filtered urine 
with about 2 c.c. of acetic acid, and 3 c.c. of potassium ferro- 
cyanid solution. Each tenth of a cubic centimeter of the 
precipitated albumin, when settled to constant reading, indi- 
cates one sixtieth of one per cent albumin by weight. This 
factor is fairly correct up to four or five tenths of a cubic cen- 
timeter of precipitate, beyond this it is of little value, and 
the albumin is best determined quantitatively by measuring 
50 or 100 c.c. of urine into a small beaker, adding a drop of 
acetic acid, and boiling, which will completely precipitate the 
albumin. It may then be filtered onto a counterpoised filter, 

then thoroughly washed, first in water, then in alcohol, 

and lastly in ether, dried at a temperature a little 
below the boiling-point of water, and weighed. 
Esbach's method may be in some instances of value, 
and is made as follows: 

The albuminometer (Fig. 21) is filled with urine 
to the line U, and then the reagent* is added to the line 
R; close the tube, mix the contents thoroughly, and 
allow to stand in an upright position for twenty-four 
hours. At the end of that time the depth of precip- 
itate may be read by the figures on the lower part 
of the tube, these figures representing tenths of one 
per cent of albumin, or grams of albumin in a liter 
of urine. If a sample of urine contains more albumin 
than is easily estimated by the centrifugal or Esbach's 
method, approximate results will be obtained by diluting with 
several volumes of distilled water, until the quantity of albumin 
precipitated is within the limit of the test. The proteoses 
occasionally occur in the urine, and are distinguished from 

* Esbach's reagent consists of picric acid. 10 grams, citric acid, 20 grams, 
and distilled water suflficient to make one liter. 



Fig. 21, 



240 URINE. 

albumin by the fact that they redissolve at a boiling tem- 
perature, and, if filtered while hot, albumin, which usually 
accompanies them, will remain on the paper, while albumose 
will separate out from the clear filtrate as it cools. 

Sugar. 

Sugar in urine represents a perverted process of oxidation 
for which the liver is largely responsible. The pancreas alsa 
often plays an important part in cases of diabetes, but just 
how this is done is not clearly known. Sugar in the urine 
does not of necessity indicate diabetes any more than does 
albumin indicate Bright 's disease. Many cases of glycosuria, 
are of a temporary nature, and respond readily to dietary 
treatment. Whenever sugar is found it is desirable to make 
tests upon both a fasting and an after-meal sample, such as 
might be obtained before breakfast and one hour after dinner. 
If the fasting sample is comparatively free from sugar it indi- 
cates that the glycosuria is of a temporary nature and due 
to faulty metabolism, rather than any organic disease of the 
liver. 

Detection. — Sugar in the urine may be detected in the 
urine by several general carbohydrate tests, as previously 
given. The one which is most valuable and most generally 
employed is FehUng's test (Exp. 54, page 175). It is best 
to modify this test by bringing the FehUng's solution to active 
ebullition, adding 5 to 30 drops of the suspected sample, and 
allowing to stand without further heating. This prevents 
possible reduction of the sugar by xanthin bases or other occa- 
sional constituents of the urine which might give misleading 
results, if the mixture were boiled after addition of the sample. 
There is less danger of trouble of this sort if the gravity of the 
urine is below normal. If it is necessary to make a rapid 
test, the mixture may be boiled after the urine is added, and 
in case the result is negative there is no need of further test; 



ABNORMAL CONSTITUENTS. 241 

if, however, a .slight rechiction ol" the copper hiolution takes 
place, it will be necessary to repeat the test, using the pre- 
caution above given. The fermentation test (Exp. 58, page 176) 
may also be used to detect the presence of sugar and, approxi- 
mately, the amount. The phenyl-hydrazine test may be used 
as a confirmatory test, or in cases where very minute (juan- 
tities are suspected. This test is considered about ten times 
as delicate as the Fehling's test, consequently it may show 
small amounts of sugar which are not detected by the more 
rapid process. Quantitatively sugar may be determined by 
the use of Fehling's solution as follows: 

If the urine contains more than a trace of albumin, this 
substance should be removed by the addition of a drop of 
acetic acid and heat; after filtration the sample should be 
cooled and restored to original volume with distilled water. 
If specific gravity of the urine is more than 1025, it should 
be diluted to ten times its volume with distilled water (urine, 
one part, water, nine). If the gravity is less than 1025 dilute 
it to five times its volume, mix, and fill a 25 c.c. burette. In 
a 250 c.c. flask place 10 c.c. each of the alkaline tartrate and 
copper sulphate solutions (Fehling's solution), and add about 
100 c.c. of distilled water. Place the flask over a Bunsen burner, 
and bring to a boil. If no change takes place after a minute or 
two boiling, add the solution from the burette gradually, until 
the precipitate becomes sufficiently dense to obscure the blue 
color of the solution. Continue to boil for one or two minutes, 
then remove from the flame and watch carefully the line directly 
beneath the surface of the Uquid, which will appear blue until 
all the copper has been reduced to the red suboxid. The solu- 
tion should be kept at the boiling-point throughout the entire 
operation, except in making the examination of the meniscus 
between the additions of the diluted urine. These additions 
must be made very carefully, and as the process nears comple- 
tion not more than one or two drops should be added at a time. 
"\^Tien the blue color has entirely disappeared, and the line of 



242 URINE. 

meniscus has become colorless, note the number of cubic centi- 
meters of dilute urine used, and calculate that in that quantity 
there is an equivalent of 0.05 gms. of glucose, in other words, 
.050 grams of glucose will exactly reduce the amount of Fehling's 
solution used, and from this fact the amount of glucose in the 
entire twenty-four hour amount of urine is easily calculated. 
If the titration is carried beyond the proper ''end point" 
the meniscus wall appear yellow instead of colorless. The 
fermentation test may be used as has been suggested to 
roughly determine the sugar present, by very carefully ascer- 
taining the specific gravity, both before and after the fermen- 
tation has taken place, and the percentage of sugar may be 
approximated by multiplying the numbers of degrees lost 
in the specific gravity by 0.25 (Ogden). The fermentation 
must be allowed to proceed under favorable circumstances 
for at least twenty-four hours, and the carbon dioxid allowed 
to escape from the solution. 

Acetone. 

Acetone may occur in the urine as a result of various patho- 
logical conditions and according to von Noorden they are all 
due to some one-side perversion of nutrition. The aceto- 
nurias attendant on diabetes, scarlet fever, pneumonia, small- 
pox, etc., are of less practical interest to the dental practi- 
tioner than those more often overlooked by the medical pro- 
fession and which indicate improper diet, possibly resulting 
in serious malnutrition. The following points may be noted: 
in advanced stages of diatetics acetone appears in the urine 
accompanied by diacetic acid. An increased ingestion of 
proteids may result in the appearance of acetone, in which 
case the direct cause is more an ''insufficient utilization of 
carbohydrates"* than the increase of proteid. Acetone may 
result from the oxidation of ,5 oxybutyric acid, diacetic acid 

* Von Xoorden's "Diseases of Metabolism and Nutrition." 



ABNORMAL CONSTITUENTS. 243 

is first formed, and subsequently the carboxyl group is replaced 
by an atom of hydrogen, as shown by the following graphic 
formula) : 

/? oxybutyria acid: CHs-CHOH-CH.-COOH. 
Diaceticacid: CH3-CO-CH2-COOH. 
Acetone: CH3-CO-CH3. 

Detection. — Acetone may be detected in the urine by the 
production of iodoform, as described under analysis of saliva 
on page 211, but it is not in this case nearly so delicate a test 
on account of the odor and acid character of the urine. A 
more useful test is known as Legal's test and is made as fol- 
lows: To a third of a test-tube full of urine add a few drops 
of a freshly prepared and fairly concentrated solution of sodium 
nitroprussid, next add 2 or 3 drops of strong acetic acid, and 
then a considerable excess of ammonia. If the contents of 
the tube are mixed by a rather rapid rotary motion without 
inverting or violent shaking, the ammonia will not reach the 
bottom of the tube, and the presence of acetone will be indi- 
cated by a violet-red band above the layer of acid Hquid. If 
much acetone is present a deep violet to a purple color is 
obtained. 

Bile. 

Bile may occur in the urine as such, due to pathologic con- 
ditions of the liver- or bile-ducts, as stated on page 223. The 
coloring-matters of the bile may also occur from causes aside 
from lesions of the liver. A urine containing bile or bile-pig- 
ments is always more or less highly colored, and upon shaking 
the foam will be of a yellow or greenish -yellow color. Albumin 
and high indoxyl accompany the presence of bile and there 
IS also usually considerable renal disturbance. It may be 
detected by carefully adding to one-half a wine-glass of the 
suspected sample a few cubic centimeters of the alcoholic solu- 



244 URINE. 

tion of iodin (tincture of iodin), a green color will be observed 
just beneath the point of contact of the two liquids (page 225). 
The test may be conveniently made by placing the iodin 
first in the wine-glass and then with a pipette introducing 
the urine beneath the iodin solution. 



Metallic Substances. 

Arsenic, mercury, and lead are the three metals which it 
may be necessary to look for in a sample of urine. The method 
for the detection of mercury, given on page 216, is applicable 
for this purpose. 

Arsenic may be detected by the Marsh-Berzelius test 
(page 11). After oxidizing all organic matter the process may 
be carried out as follows : Evaporate a liter of urine, to which 
200 c.c. of strong nitric acid has been added, to dryness; add 
to the residue, while still hot, 15 to 20 c.c. of concentrated sul- 
phuric acid. This must be done either in a large porcelain 
evaporating-dish, or else the acid added very slowly to pre- 
vent frothing over and loss of a portion of the sample. After 
the action has quieted down the whole mixture may be trans- 
ferred to a 500 c.c. Kjaldahl flask and heat applied gradu- 
ally at first, and then more strongly. It will be necessary to 
add from time to time small portions of nitric acid and pos- 
sibly a little more sulphuric; as the oxidation progresses the 
liquid in the flask becomes lighter in color and at the com- 
pletion of the process is water-white, even when the tempera- 
ture is increased so that sulphuric-acid fumes are given off. 
After cooHng the strong acid liquid is diluted with four or 
five times its volume of water, filtered if necessary to remove 
excessive amounts of earthy sulphates, and is then ready for 
the arsenic test. 

Lead. — The sample of urine to be tested for lead should 
measure at least 1000 c.c, and should be tested for iodin to 
insure the fact that the patient has been under treatment 



ABNORMAL CONSTITUENTS. 245 

with potassium ioclid to dissolve lead salts, otherwise a nega- 
tive result may be obtained when lead is actually present and 
poisoning the system. Oxidize the sample in precisely the 
same manner as when making the arsenic test up to the point 
of diluting the strong acid solution with water, then in this 
case use rather less water for the dilution, allow to cool, and 
neutralize with Squibb's ammonia, acidify c[uite strongly with 
acetic acid, and pass H2S gas into the solution. It is desir- 
able to leave the solution saturated with H2S for at least twelve 
hours, then filter, and without washing dissolve the precipitate 
in warm dilute nitric acid, evaporate the HNO3 solution to dry- 
ness, add 5 c.c. of water, make alkaline with a drop or two of 
ammonia, and again acidify with acetic acid, add a solution of 
bichromate of potash.* Allow to stand several hours, filter off 
the chromate of lead, wash several times with distilled w^ater, 
and lastly with H2S water when the lead chromate will blacken 
from the formation of lead sulphid. This stain is a super- 
ficial one and disappears upon standing, but when the process 
is conducted in this way it constitutes a very delicate and 
satisfactory test for lead in either urine or saliva. 

Urinary Sediments. 

The sediment which settles from a sample of urine upon 
standing consists normally of a slight amount of mucin and 
epithelium cells. It may contain also bacteria and a con- 
siderable variety of extraneous matter, including starch grains, 
various vegetable spores, yeast-cells, fibers from various fabrics, 
cotton, wool flax from linen, etc., diatones, scales from insects' 
wings, and other particles which may occur as dust (see Plate 
IX, Fig. 6). Under abnormal conditions the sediment may con- 
tain crystalhne elements, including uric acid and urates, phos- 
phates, oxalates, cystin, tjTosin, leucin, etc., also organized 

* Neutral chromates of potash will precipitate copper, the acid chromat^. 
precipitates lead only of the second group metals. 



246 URINE, 

elements such as epithelium, renal or other casts (Plate IX^ 
Fig. 4), blood globules, pus cells (Plate IX, Fig. 3), spermato- 
zoa (Plate IX, Fig. 2), fat, mucin (Plate IX, Fig. 5), etc. Urinary 
sediment may be thrown down from a fresh specimen by the 
use of the centrifugal machine, or it may be allowed to stand 
in a tube glass with rounded bottom for several hours, when 
the sediment settles to the bottom by gravity. If possible 
it is best to examine sediments settled in both of these ways 
as the centrifuge will show elements, such as small casts that 
would settle slowly, possibly not at all by the gravity method. 
On the other hand, the sediment allowed to settle sponta- 
neously will often give a more correct idea of comparative 
numbers of the various elements observed than when settled 
in a centrifuge-tube. A drop or two of formaline may be 
used to preserve urinary sediment, as suggested on page 227, 
but if too much of this substance is used, especially in urines 
containing high percentages of urea, a compound is liable to 
be formed which has been called formaldehydurea (Plate VIII, 
Fig. 5), which settles with the sediment and seriously inter- 
feres " with the microscopical examination. This compound 
may form sheaf- like crystals similar to tyrosin and may be 
mistaken for crystals of sodium oxalate, especially when 
examined with a low power objective." 

Uric Acid. — Uric acid is deposited from normal urine upon 
standing with an excess of free acid (HCl). Urines that 
have a high degree of acidity will also produce a like deposit, 
and the finding of uric-acid crystals does not necessarily signify 
that the crystaUization took place within the body, unless 
special care has been taken that the sample examined was 
perfectly fresh, although the tendency to deposit uric acid 
is, of course, indicated. The urine from which uric acid sepa- 
rates as such, is usually rather concentrated and of strong 
acid reaction. These crystals vary in appearance (Figs. 5 and 6, 
Plate V), but are almost always colored yellow to red. Color- 
less crystals are sometimes observed, they are usually quite 



ABNORMAL CONSTITUENTS. 247 

small, but of the peculiar whetstone shape in which this acid 
most usually crystaUizes. The presence of uric acid has prac- 
tically no effect upon the acidity of the sample, for, if the acid 
separates in a crystalline form, it is insoluble, and if it does 
not separate it is in combination as urates, possibly, of course, 
as acid urates. Uric acid exists normally in proportion to 
urea as about 1 to 50, but there is no necessary relationship 
between the quantities of the two substances, and the one 
may be diminished while the othef is increased. 

Urates. — Urates may occur as crystalline or amorphous 
precipitates. The crystaUine urates are urate of sodium rarely, 
acid urate of sodium (Plate III, Fig. 6), and acid ammonium 
urate (Plate IX, Fig. 1). The amorphous urates are of the alka- 
line bases usually sodium, and are frequently precipitated by 
lowering of the temperature after the sample has been passed, 
in such cases the urine assumes a cloudy appearance which is 
cleared up upon the application of heat. A sediment consist- 
ing of urates is usually of a pinkish color. 

Phosphates. — Phosphates in the urinary sediment may 
be amorphous or crystaUine. They are of the alkahne earths 
rather than of the alkaline metals, as the latter are soluble 
in both the acid and neutral forms. The amorphous phos- 
phates deposit with the change of reaction from acid to alka- 
line, and usually in the form of a so-called triple phosphate 
of ammonia and magnesia (Plate I, Fig. 4). This salt crys- 
tallizes in two forms- the prismatic form is the ultimate 
form, that is, if the crystallization takes place very slowly, 
the prismatic form is the one in which the salt is thrown out. 
If it takes place rapidly it may be precipitated in the feathery 
form, but this slowly changes over to the prismatic form. The 
acid phosphates may be precipitated closely resembHng the 
acid urates (Plate III, Fig. 6), but may be distinguished 
from them by their ready solubiUty in acetic acid and failure 
to produce after solution in acetic acid any crystals of uric 
acid which are obtained from the urates. 



248 URINE. 

Lacto-phosphate. — This name, for certain crystalline com- 
pounds which have been formed by the action of lactic acid 
and calcium phosphate^ may or may not strictly represent the 
chemical product of such action. It has been criticised, but 
as no better name has been suggested for salts produced in this 
wa}^, we shall use it. These are soluble salts, and are found 
in urine only by evaporation of a drop of the sediment and 
examination with polarized light. When found in the urine, 
the significance is quite different from that when found in the 
sahva, as in the urine they may possibly be formed from lac- 
tates, which indicate a faulty action of the liver, and of course 
they have no connection with tooth erosion. The lactates fur- 
nish evidence of similar character. 

Oxalates. — Oxalates if found in the sediment usually occur 
as calcium oxalates. These crystals assume a variety of forms, 
as shown in Fig. 1, Plate III. Sodium oxalate (Fig. 3, 
Plate III) may occur in the urine (not, however, in the sedi- 
ment), and is detected only by evaporating a drop of the clear 
liquid and examination with polarized light. Dr. Kirk claims 
that an oxaluria may be in this way detected for a consider- 
able time before the appearance of the oxalate of lime crys- 
tals, and hence such examination becomes a valuable aid to 
diagnosis. 

Cystin. — Cystin occurs as six-sided plates. It is a com- 
paratively rare crystal, and indicates insufficient oxidation 
particularly of the organic sulphur compounds. 

Epithelium. — Epithelium occurs in the urinary sediment 
from any part of the urinary tract. In the male urine it is 
much easier to determine the character of the epithehum 
than in the female, as in the latter the comparatively large 
amount of mucus surface, from which epithelium may be 
gathered, furnishes a great variety of forms which are, of 
course, without clinical significance. The epithelium from 
the vagina may be quite readily distinguished as very large 
cells with small nuclei, lying usually in masses overlapping 



ABNORMAL CONSTITUENTS. 249 

one another but with comparatively shght density. Renal 
epithelium may be found as small, round cells, differing but 
slightly in size from a leucocyte. They may be a little larger, 
a httle smaller, or about the same size. They are round, and 
more or less granular in appearance. 

EpitheUum from the bladder varies considerably, but the 
majority of cells would properly come under the general head 
of squamous epithelium, rather large and flat with a distinct 
nucleus of medium size. EpitheUum from the neck of the 
bladder in male urine are quite typical, being round and com- 
paratively dense with a prominent nucleus. They aie four 
or five times the size of a leucocyte and, in cases of irritation 
at the neck of the bladder, are usually present in considerable 
numbers and of quite uniform appearance. 

Renal casts consist of molds formed within the tubules of 
the kidneys which retain the form of the tubules after expul- 
sion into the bladder. According to Ogden the most probable 
theory of their formation is " that they are composed of coagul- 
able elements of blood that have transuded into the renal 
tubules, through pathologic lesions of the latter, and have there 
sohdified to be later voided with the urine, as molds of the 
tubules." Casts are termed blood casts, pus casts, epithelium 
or fat casts according as these elements may adhere with more 
or less profusion to the cast itself. Pure hyaline casts are 
pale, perfectly transparent cylinders, with at least one rounded 
end which can be plainly seen and may occur occasionally in 
urine from perfectly healthy individuals. Fibrinous casts 
are highly refractive and when seen by white light are of a 
yellowish color and indicate acute renal disturbance. Waxy 
easts resemble the so-called fibrinous as regards density, but 
they have no color, and usually indicate advanced and serious 
stages of kidney disease, while the presence of fibrinous casts 
have no necessarily serious significance. 

Blood and Pus are readily recognized under the micro- 
scope after a very little practice. The blood disks are cir- 



250 URINE. 

cular and show a characteristic biconcavity in the alter- 
nate shading of the edge and center by slight changes of 
focus. The red corpuscles usually show a shade of color by 
white light. The pus corpuscles or leucocytes are larger than 
the red corpuscles, and are granular in appearance. Treat- 
ment with acetic acid destroys the granular matter and brings 
into prominence the cell nuclei two or three in number. If 
the leucocytes are free and scattered they should not be regarded 
as pus but be reported simply as an excess of leucocytes, if 
they are very numerous and occur in clumps they constitute 
pus. 

Spermatozoa. — Occasional spermatozoa may be found in 
sediment from either male or female urine and are without 
clinical significance. If persistent and in considerable num- 
bers, seminal weakness is indicated (Plate IX, Fig. 2). 

Fat occurs in urinary sediment as small globules highly 
refractive and varying greatly in size. They are frequently 
adherent to cells or to casts. Fatty casts indicate a fatty 
degeneration which may or may not result from chronic disease. 
Fat may be demonstrated by staining with osmic acid which 
is reduced by the double-bonded fatty constituent (olein), 
leaving a black deposit which stains the globule. 

Mucin appears in the sediment as long and more or less 
indistinct threads. An excessive amount usually indicates 
irritation of some nmcus surface. The source would have to 
be determined by other more characteristic elements (Plate IX^ 
Fig. 5). 

The salts which may be obtained by evaporation of a drop 
of clear urine and detected by the micropolariscope are simi- 
lar to those occurring in the saliva; sodium oxalate is prob- 
ably most frequently found. If the gravity is above normal 
the urea often crystallizes, making it somewhat difficult to 
pick out the abnormal crystalHne constituents. Phosphates 
are also usually observed, but these crystals are large and with 
square corners, not easily mistaken for anything else. 



ABNORMAL CONSTITUENTS. 251 

Interpretation of Results. 

As stated at the beginning of the chapter on urine, our 
object has been the study of this secretion from the stand- 
point of general metabolism, rather than with a view to differ- 
entiate various forms of renal disease, and while it is important 
that the presence of renal disease should be recognized, its 
further investigation constitutes a proper study for the physician 
rather than for the dentist, and when such conditions are found 
to exist a patient's physician should be apprised of the fact. 

The discussion of a few examples based upon actual analysis, 
made during 1905 and 1906, may serve to show deductions 
which may be drawn from analyses of saliva and urine. 

No. 1.* 
ITRINE. Name. Date, Feb. '00. Phys. Dr. C. A. J. 



24 h, Am't. = 2000 c.c. Sp. Gr.= 1013 



Grams in X. 
24 hours. 

17.6 (28.0). 

.68 ( 0.5> 

9.1 (lo.oy 

1.8 ( 2.7) 



Color=N. Reaction = Ac. + Urea =0.88 (2.0) 

Uph. = Sl.- Uric Ac. = 0.034 (0.033) 

'Ind. =+ E. Phos. =- Chlor. =0.455 (0.67) 

A. Phos. =- Phos. Ac. = 0.09 (0.18) 
Acetone = Abs. Sugar = Abs. 
Alb. = SI. possible trace. Uric Ac. to Urea= 1 to 24 (50) 

Sediment. Occasional leucocytes, few neck of bladder-cells, an excess of mucin. 
(The numbers in brackets are the average normal.) 

ANALYSIS OF SALIVA. 
Dr. C. A. J. February, 1906. 

Appearance = cloudy. Odor= slight. 

Reaction = strongly acid. Specific gravity = 1003. 

Mucin = slight. Albumin = marked. 

Ammonia = increased, but inferior to Glycogen = negative. 

sulphocyanate which is very high, 
Chlorin= normal or slightly increased. 
Soluble salts = lactates, alkaline chlorids. 
Abnormal constituents = lactic acid. 
Sediment= heavy, excess of leucocytes, 

mucin, and squamous epithelium. 
Indicated diathesis= hyperacid. 

* The abbreviations used in this analysis are as follows: N= normal, Ac,= 
acid, Sl. = shght. The minus sign= diminished or decreased, the plus sign = ex- 
cessive or increased, Abs. = absent. 



252 URINE. 

As we study these analyses we notice first in the urine 
an increased quantity with low urea. These things accompany 
chronic kidney disease, but inasmuch as in this case we find 
no casts in the sediment, and no more albumin than can be 
accounted for by the slight irritation at the neck of the bladder, 
we consider the dilution unimportant. The uric acid is high 
in proportion to the urea, and the chlorin being nearly nor- 
mal for the twenty-four-hour amount would indicate a full 
diet with perverted oxidation. These indications are of 
probabilities rather than positive conclusions, although in 
this particular case the actual facts were as indicated. The 
high indoxyl in the absence of any acute disease would indi- 
cate an increased putrefaction in the small intestine, probably 
due to defective intestinal digestion. 

The condition of the saliva, together with the urine analysis, 
would indicate a condition favorable to erosion of the teeth 
and the development of pyorrhoea. It was found that the 
patient was not suffering from erosion of the teeth, except in 
a very slight degree, but the evidences of pyorrhoea were quite 
marked at the time of the first examination some weeks before 
the analyses were made. A reduction of the nitrogeneous 
diet and proper systemic treatment to correct the intestinal 
trouble, and to increase the general oxidations, would without 
doubt have a beneficial effect upon the conditions of teeth 
and gums, although at the time of this writing sufficient time 
has not elapsed to enable us to give positive results. 

No. 2. 
URINE. Name. R. R. Date, April, '05. Phys. 



24 h. Am't.= 1200 c.c. 


Sp. Gr. 


= 1023 


N.% 


Grams in 
24 hours. 


N. 


Color=Sl. high Reaction = Ac. 


Urea 


= 2.27 


(2.0) 


25.24 


(28.0) 


Uph. = N. 


Uric A. 


= 0.051 


(0.033) 


0.61 


( 5) 


Ind. =N E Phos. =N. 


Chlor. 


= 0.834 


(0.67) 


10.1 


(10.0) 


A. Phos. =N. 


Phos. A. 


= 0.112 


(0.18) 


1.3 


( 2.7) 


Acetone =Abs. 


Sugar 


= Abs. 









Alb. =S1. possible trace. 

Sediment. — Numerous large calcium oxalate crystals, occasional uric-acid crys- 

tals, excess of mucin, rarely a blood globule. 

(The numbers in brackets are the average normal.) 



ABXORMAL CONSTITUENTS. 253, 

The saliva accompanying this sample indicated a hyper- 
acid diathesis and a sHght amount of pus in the sediment, 
otherwise nothing abnormal. In this sample we notice a 
concentrated urine with a tendency to precipitation of crys- 
talline elements which have apparently produced a slight 
irritation of the urinary passages, as indicated by the blood 
globules, and the slightest possible trace of albumin. The 
patient in this case was a young man in good general health, 
a student at the Dental School. A beginning pyorrhoea had 
been noticed and, as a result of information gained by this anal- 
ysis, the red meat, coffee, and other uric -acid producing foods 
were wholly eliminated from the diet, and improvement of 
the conditions of teeth and gums followed. 







No. 3. 








URIXE. 


Name. F. 


J. Date, Dec. '05 


Phys. Dr. R. 




24 h. Am't.= 


= 2200 c.c. 


Sp. Gr. = 1026 


N.% 


Grams in 
24 hours 


X. 


Color = N. 


Reaction = Ac. 


+ Urea =2.65 


(2.0) 


58.3 


(28.0) 


Uph. =S1 - 




Uric Ac. =0.047 


(0.033) 


1.03 


( 0.5) 


Ind. =S1.- 


E. Phos. = N. 


Chlor. =0.625 


(0.67) 


13.7 


(10.0) 


Bile =Abs. 


A. Phos. = N. 


Phos. Ac. = 0.16 


(0.18) 


3.5 


( 2.7) 



Acetone = very slight trace Sugar= slight trace present. 
Alb. = SI. possible trace. 

Sediment. — Calcium oxalate crystals very numerous, occasional leucocyte, occa- 
sional blood globule with rarely a hyahne cast. 

(The numbers in brackets are the average normal.) 

This urine is from a patient with a tendency to diabetes 
and is living almost exclusively on a proteid diet. This accounts 
for the high uric acid and high urea. There is a slight irrita- 
tion of the kidneys which is secondary to the glycosuria. There 
was no trouble with the teeth, no examination of saliva was 
made. 

The following sample indicates a chronic disease of the kidney, 
and it was thought wise to have the day and night twelve-hour 
quantities measured separately as, in cases of chronic kidney 
disease, the night quantity usually exceeds the day, and this 
fact is often a valuable aid in determining the character of 



254 URINE. 

kidney disturbances. The metabolism in this case is good, 
the nephritis being only at an early stage. 







No. 4. 








URINE. 


Name. Miss D. Date, Nov 


'05. 


Phys. W. 


K. 


24 h. Am't.= 


= 2500 c.c. 


Sp. Gr.-1012 


N.% 


Grams in 
24 hours 


N. 


Color=Pale 


Reaction N. 


Urea =1.01 


(2.0) 


25.25 


(28.0) 


Uph. = - 




Uric Ac. =0.020 


(0.033 


0.50 


( 0.5) 


Ind. =- 


E. Phos.= - 


Chior. =0.315 


(0.67) 


7.87 


(10.0) 




A. Phos.= - 


Phos. Ac. = 0.90 


(0.18) 


2.25 


( 2.7) 




Acetone = Abs. 


Sugar = Abs. 









Alb. =S1. trace 

Sediment. — Squamous epithelium with several hyaline and fine granular casts. 
(The numbers in brackets are the average normal.) 

As seen by these examples, it is necessary to take the whole 
analysis into consideration, often in conjunction with an 
analysis of the saliva, in order to know just what the system is 
doing, and whether there is possible systemic derangement which 
may have an important bearing on conditions found in the oral 
cavity. Experience and study will alone enable one to correctly 
interpret the results of such analyses, but it has been our aim to 
give sufficient groundwork for the prosecution of such study, 
and to show that in many cases the knowledge derived from 
thorough examinations may be of the greatest importance 
in the successful treatment of diseased conditions. 



APPENDIX. 



Preparation of KCNO. — Melt in an iron ladle, of at least 
50 c.c. capacity, five grams of commercial potassium cyanicl, 
and stir in gradually 20 grams of litharge. When the entire 
amount has been added, pour the mass out upon an iron plate, 
and allow to cool. Separate as far as possible the reduced 
lead from the potassium cyanid that has been formed, powder 
the latter and dissolve in 25 c.c. of cold H2O. Filter if necessary 
and purify by repeated crystallization. 

Synthesis of Urea.— Add to the filtered solution of KCNO 
(above) a cold saturated solution of ammonium sulphate, con- 
taining at least six grams of (NH)2S04. Heat the mixture 
slowly on a water-bath at a temperature of 60° C, and main- 
tain at that point for one hour. By this process ammonium 
€yanate is formed and then changed to urea, which may be 
obtained in an impure stat6 by evaporating the solution to dry- 
ness on a water-bath, extracting the residue with hot, strong 
alcohol. The urea will crystalhze from the alcohol as it cools. 

Preparation of Phenoldisulphonic Acid. — Phenoldisulf 
phonic acid, for estimation of nitrates in water analysis, may 
be prepared by heating on a water-bath for several hours 
a mixture of 555 grams of concentrated sulphuric acid and 
45 grams of pure carbolic-acid cr3^stals. 

Isolation of Glycogen CCeHioOs)/!. — Use a liver taken 
from an animal just killed, or, if the season permits, oysters 
just removed from the shell. Cut one-half, as rapidly as pos- 

255 



256 APPENDIX. 

sible, into small pieces, and throw it into four times its weight 
of boiling water, slightly acidulated with acetic acid. After 
boiling the first portion for a short time, remove the pieces,, 
grind in a mortar with some sand, return to the water, and 
continue the boiling for several minutes. Filter while hot. 
The opalescent solution thus obtained is an aqueous solu- 
tion of glycogen and other substances. 

If a purer solution is desired, continue as follows: Add 
to the filtrate alternately a few drops of HCl and potassio- 
mercuric iodid, until a precipitate of proteid ceases to form. 
This may be determined more conveniently by filtering off 
a small portion of the Hquid from time to time, and adding 
to the clear filtrate the HCl and potassiomer curie iodid. When 
the precipitation of the proteids is complete, filter, and to the 
milky filtrate add double its volume of alcohol; the glycogen 
will precipitate as a white powder. Filter this off, wash with 
66 per cent alcohol (one part of water to two of alcohol), and 
dissolve in water. 

Preparation of Mucin Solution. — Cut a portion of a navel- 
cord into small pieces. Shake in a flask with water, changing 
the water several times. This removes salts and albumin. 
Extract for twenty-four hours with Hme-water or baryta-water 
in a corked flask. Filter. To filtrate add acetic acid, which 
precipitates the mucin. Let settle, filter, and wash with water. 

Mucin may also be prepared from the saliva by precipi- 
tation with acetic acid. 

Preparation of Cystin, Tyrosin, and Leucin. 

Cystin. — 1. Boil 200 grams of hair, cleaned by washing 
with dilute HCl and then with ether, with 600 c.c. of con- 
centrated HCl (specific gravity, 1.19) for four hours in a three- 
Hter flask with condenser on a sand-bath in hood. Then let 
cool. 

2. Add concentrated NaOH solution (750 c.c. H2O, 500' 
grams NaOH) till the reaction is only faintly acid. 



APPENDIX. 257 

3. Add to the solution, which has begun to boil on neu- 
tralization, plenty of animal charcoal, and boil three-quarters 
of an hour. 

4. Filter hot, being careful to moisten filter and funnel 
with hot water, to pn^vent funnel from cracking. 

5. The filtrate should be faintly yellow. On cooling, a 
crystalline precipitate forms, mainly cystin, with some tyrosin 
and leucin. If this is not the case, or if it is slight, it must be 
concentrated. Save the filtrate, which is to be worked up for 
tyrosin and leucin later, and add the filtrate from 6 for work- 
ing up tyrosin later. 

6. After standing overnight filter off the precipitate. 

7. Dissolve this precipitate in 350 c.c. of hot 10 per cei>t 
NH4OH (hood) and let cool. Then cool thoroughly with 
finely chopped ice or with snow. Filter off any tyrosin that 
may have precipitated, and combine it with the filtrate of 6. 

8. Add carefully glacial acetic acid, being careful not to 
acidify. The precipitate is a mixture of tyrosin and cystin. 
Filter. 

9. Make quite acid with glacial acetic acid. The precip- 
itate is almost pure cystin. Let stand twenty-four hours. 
Then filter, and wash with H2O and alcohol. 

10. Recrystallize by redissolving in as little hot 10 per 
cent ammonia as is necessary to effect solution, cooling and 
precipitating with glacial acetic acid. 

The preparations should be pure and contain no tyrosin, 
for which test may be made with Millon's reagent. 

Reactions. — Put a trace of cystin into a test-tube with 
some dilute NaOH and a httle lead acetate. Boil. H2S is 
formed because S is split off. 

Tyrosin. — 1. Concentrate the neutralized filtrate of 6 of 
cystin preparation till, on cooHng, tyrosin crystaUizes out. 

2. Filter, and save filtrate for the preparation of leucin. 

3. Dissolve the tyrosin crystals in very little hot water. 

4. Add amyl alcohol till a heavy precipitate forms. 



258 APPENDIX. 

5. Filter precipitate. 

6. Redissolve in very little hot water, and let crystallize 
out by cooling. 

Examine crystals under the microscope. 
Test with Millon's reagent. 

Leucin.— 1. Take the filtrate of 2 in the preparation of 
tyrosin, and evaporate to dryness on the water-bath. 

2. Extract with alcohol. 

3. On standing the leucin crystaUizes out of the alcohoUc 
extract as it evaporates. 

4. Filter, and dry the crystals. 
Examine under the microscope. 

Preparation of Fehling*s Solution. — The Fehling's solu- 
tion recommended for experiments in this book is one-half 
the strength frequently employed, and is prepared in separate 
solutions as follows: Dissolve 34.639 grams of pure crystal- 
lized copper sulphate in water, and make solution up to one 
Hter. This constitutes the first part of the reagent. The 
second part may be made by dissolving 173 grams of Rochelle 
salt and 52.7 grams of caustic soda (NaOH) in water and make 
up to one liter. When prepared in this way 10 c.c. of each 
of these solutions mixed together will be reduced by 0.05 
gram of glucose. 

Formula for Magnesia Mixture. — 125 grams of ammonium 
chlorid, 125 grams of magnesium sulphate, dissolved in suffi- 
cient water to make one liter of solution, then add 125 c.c. 
of strong ammonia water. 

Phenyl-hydrazine Solution. — 1 gram phenyl-hydrazine hy- 
drochloride and 2 grams sodium acetate dissolved in 10 c.c. 
water. 

Barfoed*s Reagent. — Dissolve one part of copper acetate in 
fifteen parts of water; to each 200 c.c. of this solution add 
5 c.c. of acetic acid containing 38 per cent of glacial acetic acid. 

Millon's Reagent. — To one part of mercury add two parts 
nitric acid of specific gravity 1.4, and heat on the water-bath 



APPENDIX. 259 

till the mercury is dissolved. Dilute with two volumes of 
water. Let the precipitate settle, and decant the clear fluid. 

Dimethyl-amido-azobenzol. — 0.5 per cent alcoholic solution. 

Nessler's Solution. — This is an alkaline solution of mercuric 
iodid, made by dissolving 35 grams of potassium iodid in 
about 200 c.c. of water. Dissolve 17 grams of mercuric 
chlorid in 300 c.c. of hot water. Add the first solution of KI 
to the second, until the precipitate at first formed is nearly all 
redissolved. If the precipitate should entirely dissolve, add a 
few c.c. of a saturated solution of mercuric chlorid, until a 
slight permanent precipitate is obtained. After the mixture 
is cold, make up to one liter with a 20-per-cent solution of 
caustic potash. Allow to settle and use the clear solution. 

Gunzburg*s Reagent. — Phloroglucin, 2 grams; vanillin, 1 
gram; alcohol, 100 c.c. 

Tropseolin 00. — Saturated alcoholic solution. 

Congo Red. — 2 per cent aqueous solution. 

Uffelmann's Reagent— Mix 10 c.c. of a 4-per-cent solution 
of carbolic acid with 20 c.c. of water, and add a drop or two 
of ferric chlorid. 

Bromine Solution for Urea. — 125 grams KBr and 125 grams 
Br to one hter water. 

NaOH Solution for Urea. — A 40-per-cent solution. 

Picric-acid Solution (Esbach's Reagent). — Picric acid, 10 
grams; citric acid, 20 grams; add water up to one liter. 

Tincture lodin for Bile Test. — Dilute until just transparent 
in test-tube. 

Silver-nitrate Solution. — Drop solution, 1:8; quantitative 
solution, 29.075 grams AgNOs, niade up to one liter with water. 
1 c.c. of this solution corresponds to 0.01 gram NaCl or 0.00607 
gram CI. 

Ferric Chlorid. — 2.5 per cent. 

lodin Solution. — 10 grams iodin, 20 grams KI, made up to 
one liter with water. 

Gram's Solution. — Same as lodin Solution above. 



260 



APPENDIX. 



CUSO4 Solution. — 1 per cent for Biuret test. 
K4Fe(CN)6 Solution.— 10 per cent. 
HgCl2 Solution. — 5 per cent. 

INTERNATIONAL ATOMIC WEIGHTS. 1906. 



Aluminum. . . 
Antimony. . . 

Argon 

Arsenic 

Barium 

Bismuth 

Boron 

Bromine 

Cadmium. . . , 
Caesium, . . . , 

Calcium 

Carbon 

Cerium 

Chlorine. . . . , 

Chromium. . , 
Cobalt. ... .. 

Columbium. . 

Copper 

Erbium. . . . , 
Fluorine. . . . 
Gadolinium. . 

Gallium 

Germanium. , 
Glucinum. . . , 

Gold 

Helium 

Hydrogen. . . 

Indium , 

Iodine , 

Iridium. . . . , 

Iron , 

Krypton, . . . , 
Lanthanum. . 

Lead 

Lithium. . . . , 
Magnesium, . 
Manganese. ., 
Mercury, , . ,, 
Molybdenum, 



Al 

Sb 

A 

As 

Ba 

Bi 

B 

Br 

Cd 

Cs 

Ca 

C 

Ce 

CI 

Cr 

Co 

Cb 

Cu 

Er 

F 

Gd 

Ga 

Ge 

Gl 

Au 

He 

H 

In 

I 

Ir 

Fe 

Kr 

La 

Pb 

Li 

Mg 

Mn 

Hg 

Mo 



0=16. 



27.1 

120.2 

39.9 

75.0 



137.4 
208.5 

11.0 

79.96 
112.4 
132.9 

40.1 

12.00 
140.25 

35.45 

52.1 

59.0 

94. 

63.6 
166. 

19. 
156. 

70. 

72.5 
9.1 
197.2 
4. 

1.008 
115. 
126.97 
193.0 

55.9 

81.8 
138.9 
206.9 
7.03 

24.36 

55.0 
200.0 

96.0 



H=l. 



26.9 
119.3 

39.6 

74.4 
136.4 
206.9 

10.9 

79.36 
111.6 
131.9 

39.7 

11.91 
139.2 

35.18 

51.7 

58.55 

93.3 

63.1 
164.8 

18.9 
154.8 

69.5 

72. 

9.03 
195.7 
4. 

1.000 
114.1 
126.01 
191.5 

55.5 

81.2 
137.9 
205.35 
6.98 

24.18 

54.6 
198.5 

95.3 



Neodymium. . . 

Neon 

Nickel, o 

Nitrogen 

Osmium 

Oxygen 

Palladium . . . , 
Phosphorus. . . 

Platinum 

Potassium, . . . 
Praseodymium 

Radium 

Rhodium 

Rubidium 

Ruthenium. . . . 

Samarium 

Scandium 

Selenium 

Silicon 

Silver 

Sodium 

Strontium 

Sulphur 

Tantalum 

Tellurium 

Terbium 

Thalhum 

Thorium 

Thuhum 

Tin 

Titanium 

Tungsten 

Uranium 

Vanadium. . . . 

Xenon 

Ytterbium. . . . 

Yttrium 

Zinc 

Zirconium 





0=16. 


Nd 


143.6 


Ne 


20. 


Ni 


58.7 


N 


14.04 


Os 


191. 





16.00 


Pd 


106.5 


P 


31.0 


Pt 


194.8 


K 


39.15 


Pr 


140.5 


Ra 


225. 


Rh 


103.0 


Rb 


85.5 


Ru 


101.7 


Sm 


150.3 


Sc 


44.1 


Se 


79.2 


Si 


28.4 


Ag 


107 . 93 


Na 


23.05 


Sr 


87.6 


S 


32.06 


Ta 


183. 


Te 


127.6 


Tb 


160. 


Tl 


204.1 


Th 


232.5 


Tm 


171. 


Sn 


119.0 


Ti 


48.1 


W 


184. 


U 


238.5 


V 


51.2 


Xe 


128. 


Yb 


173.0 


Yt 


89.0 


Zn 


65.4 


Zr 


90.6 



H = l. 



142.5 

19.9 

58.3 

13.9a 

189.6 

15.88 
105.7 
30.77 
193.3 
38.85 
139.4 
223.3 
102.2 
84.9 
100.9 
149.2 
43.8 
78.6 
28.2 
107.11 
22.88 
86.94 
31.82 
181.6 
126.6 
158.8 
202.6 
230.8 
169.7 
118.1 
47.7 
182.6 
236.7 
50.8 
127. 
171.7 
88.3 
64.9 
89.9 



INDEX. 



Acetaldehyd, 133 

Acetamid, 150 

Acetanilid, isocyanid test for, 153 

Acetates, test for, 49 

Acetic acid, 145 

Acetic acid, N/10 factor, 96 

Acetic acid, test for (Acetates), 49 

Acetic ether, 138 

Acetone, 134, 211 

detection of (Legal's test), 243 

in blood, indication of, 135 

in saliva, 209 

test for, in saliva, 211 

test for, in urine, 243 
Acetylene, 127 

Exp. 7 and 9. 129, 130 

series, 127 
Acetyl urea, 155 
Achroodextrin, 173 
Acid, acetic, 145 

albuminates, experiment with, 188 

asparaginic, 149 

benzoic, 164 

boric, test for, 48 

carbolic. 111 

citric. 144 

diacetic, 147 

dibasic, 145 

dibasic amido, 149 

fatty, 143 

formic, 144 

fulminic, 153 

glacial acetic, 145 

group I. 42 

group II, 42, 45 

group 111, 42, 47 

group II and III, preliminary 
examination of, 44 

hippuric, 148 



Acid, hydrocyanic, 152 

isocyanic, 153 

lactic, 146 

malic, 144 

malonic, 144 

oleic, 145 

oxalic, 145 

oxahc test, on platinum, 52 

oxypropionic, 146 

parabanic, 156 

paralactic, 147 

phenol sulphonic, 163 

phenyl sulphuric, 163 

picric, 164 

pyrotartaric, 149 

salicyhc, 164 

sarcolactic, 147 

succinic, 146 

sulphocyanic, 153 

tartaric, 144, 148 

thiocyanic, 153 

trichloracetic, 118 

uric, 156 
Acidimetry, 94 

Acidity of gastric contents deter- 
mined, Exp. 44, 221 
Acids, analytical reactions of, 41 

basicity of organic, 143 
Acidum hydrocyanicum dilutum, 152 
Acoin, 109 

Acrj'lic-acid series, 144 
Addition products, 127 
Adenin, 157 
Adrenaline, 109 
Adrenol, 109 

Adjacent substitution products. _o2 
Adnephrin, 109 
iEther, 136 
Alabaster, 30 

261 



262 



INDEX. 



Albumin, 183 

in saliva, 206, 213 

in urine, 237 

nitric-acid test, 186 

picric-acid test, 186 
Albuminates, 186 
Albuminoids, 183 
Albuminometer (Esbach's), 239 
Albuminoscope, 238 
Albumose, 188, 189 
Alcohol, 130 

ethyl, 131 

methyl, 131 
Alcohols, primary, secondary, and 

tertiary, 131, 132 
Aldehyd, 133 
Aldehyds, 132 
Aldose, 171 

Algaroth, powder of, 73 
Aliphatic hydrocarbons, 126 
Alkah albuminates, experiment with, 

21, 188^ 
Alkali aluminates, 21 
Alkali metals, 33 
Alkalimetry, 94 
Alkahne earths, 29 
Alkalinity of saliva, 217 
Alloxan from uric acid, 158 
Alloy, definition, 64 
Alloys, anneahng of, 66 

properties of, 64 
Allylene, 128 
Alum, 21 
Aluminates, 21 
Aluminum, 21 

blowpipe test, 56 
Aluminum bronze, 64 
Aluminum salts, reactions of, 21, 22 
Aluminum, solders for, 80 
Amalgam alloy, definition, 64 
Amalgam, crushing strength of, 74 

effect of various metals, 71, 72 

flow of, 68 

test for, 73 
Amalgams, 67 
Amido-acetic acid, 148 
Amido acids, 148 
Amido-benzene, 163, 165 
Amido-isobutyl-acetic acid, 149 
Amido-valerianic acid, 149 
Amids, 150 
Amins, 149 

Ammonia nitrate on platinum, 52 
Ammonia, test for, in saliva, 210 
Ammonium amalgam, 69 
Ammonium carbonate, 154 



Ammonium isocyanates, source of 

urea, 154 
Ammonium - magnesium - phosphate 

microchemical formation, 108 
Ammonium phosphomolybdate, mi- 
crochemical formation of, 108 
Ammonium-platinic chloride, micro- 
chemical formation of, 108 
Ammonium salts, closed-tube test, 54 
Ammonium, salts of, 35 
Ammonium salts in saliva, 207 
Amyl acetate, 139 
Amyl alcohol, 131 
Amyl butyrate, 139 
Amyl hydrid, 125 
Amyl nitrate, 139 
Amylopsin, 222 
Anaesthetics, local, 108 
Analysis in dry way, 50 
Analysis of gastric contents, 218 
Analysis 

of group I, 5 

of group II (a), 17 

of group II (6), 18 

of group III, 22 

of group IV, 27 

of group V, 31 

of group I, outline, 38 

of group II, outline, 38 

of group III, outline, 39 

of group IV, outhne, 39 

of group V, outline, 40 

of group VI, outhne, 40 

of groups III, IV, V, phosphates 
present, 36, 39 

of sahva, 210 

of teeth and tartar, 120 
Analytical groups, 2 
Anesthol, 109 
Aniline, 163, 165 

isocyanid test for, 153 
Annealing of gold, 67 
Antialbumid, 184 
Antifibrin, isocyanid test for, 153 
Antimonic oxychlorid, 13 
Antimony, 13 

blowpipe test, 55, 56 

closed-tube test, 54 

effects of, in alloys, 71 

salts, reactions of, 13 
Appearance of saliva, 211 
Appendix, 255 
Aqua regia, 15 
Argentum, 3 
Argyrol, 51 
Arington's alloy (S. S. White), 73 



INDEX. 



263 



Arsenic, 9 

closed-tube test, 54 

Fleitmann's test, 11 

Gutzeit's test, 9 

in urine, 244 

Marsh- Berzelius test, 11 

Marsh's test, 13 

reactions, 9 

Reinsch's test, 10 

salts, 12 

tests, 10, 11, 12 

trioxid, 9 

voknnetric determination of, 99 
Arsenical pyrites, 9 
Arsenic and antimony mirrors, tests, 

14 
ArseiiiJe of silver, 11 
Arseinous acid, 9 
Arsenious salts, 9 
Arsine, 12 

Artificial enamel, 78 
Asparaginic acid, 149 
Aspartic acid, 149 
Atomic weights, table of, 260 
Atropine, 110 

test for, 110 
Aurum, 15 
Autolysis, 201 

Babbitt's metal, 85 
Barfoed's solution, 172 
Barfoed's test, Exp. 57, 175 
Barium, reactions, 29 
Base metals, 1 
Bastard metals, 1 
Bead tests, 57 

with borax, 57 

with microscosmic salts, 57 
Bell metal, 64 
Benzaldehyd, 164 
Benzene, 161, 162 

preparation, Exp. 42, 167 

ring, 161 
Benzoated lard, 164 
Benzoic acid, 164 
Benzol, 161 
Benzoyl glycocoll, 165 
Beryllium in dental cement, 78 
Beryllium, separation from zinc and 

aluminum, 78, 79 
Beta-Eucain, 113 
Bile, 222 

action of, in digestion, 225 

in urine, 243 

pigments (Gmelin's test), 225 

salts, separation of, Exp. 154, 224 



Bilirubin, 222 
Biliverdin, 222 
Binary amalgams, 69 
Biogen, 114 
Bismuth, 8 

blowpipe test, 55, 56 

effect of, in alloys, 71 

ochre, 8 

salts, reactions, 8 
Biuret, 155 

reaction, 185 
Black wash, 4 
Blood, 193 
Blood corpuscles, chemistry of, 194 

size of, 195 
Blood plasma, 193 
Blowpipe tests on plaster, 55, 56 
Blowpipe tests with cobalt nitrate, 

56 
Blowpipe tests with KI and S, 56 
Blowpipe tests with tetrachlorid of 

tin, 56 
Boas' reagent, 220 
Bone, 195 
Borates, 47 
Borax, 109 

beads, 24 
Boric acid, test for, 48 
Brass, solder for, 81 
Brick-dust deposit, 157 
Britannia metal, 64 
British gum, 174 
Bromids, test for, 44 
Bromin solution, 259 
Bromin, test for, in organic sub- 
stances, 124 
Bromoform, 129 
Burettes, 93 
Butan, 125 

Butter-fat, composition of, 139 
Butylene, 127 
Butyrates, 139 
Butyric acid, 145 

test for, in gastric contents, 138 
Butyrin, 139 

Cadaverin, 150 
Cadmium, 8 
Cadmium amalgam, 70 
Cadmium, blowpipe test, 56 

effect of, in amalgam alloy, 70 

salts, reactions of, 9 

oxalate, microchemical formation 
of, 107 
Caffein, 157 
Calamine, 26 



264 



INDEX. 



Calcium oxalate, microchemical for- 
mation of, 107 
Calcium salt reactions, 30 
Calcium sulphate, 59 
Calcium, test for, in teeth, 121 
Calc-spar, 30 

Calculations of standard solutions, 95 
Calomel, 4 
Camphors, 177 
Cane-sugar, 172 
Carat, definition, 83 

rule to determine, 84 
Carbids, 51 
Carbinol, 131 
Carbocyclic compounds, definition, 

166 
Carbohydrates, 122 

classification of, 170 

Molisch's test for, 175 
Carbolic acid, 111, 163 

distinguished from creosote, 112 

microchemical test. 111 
Carbon, test for, in organic matter, 

123 
Carbonates in saliva, 209 
Carbonates, test for, 43 

titration of, 95 
Carbonic acid, test for, in teeth, 120 
Carnallite, 33 
Carnin, 199 
Casein, 190 
Caseinogen, 190 
Cassiterite, 14 
Cellulose, 174 
Cement, composition of, 119 

dental, 75 

metaphosphate, 75 

oxychlorid, 77 

oxyphosphate, 75 

oxy sulphate, 77 

solubility of, 76 

tin, 77 
Chalk, 30 

Chase's copper amalgam alloy, 73 
Chase's incisor alloy, 73 
Checkerberry, essence of, 165 
Chili saltpetre, 34 
Chloral, 133 
Chloralhydrate, 111, 133 

test for, 111 
Chlorates, test for, 49 
Chlorethyl, 128 
Chloretone. 108, 111 

microchemical test for, 112 
Chlorids, 46 

in urine, 233 



Chlorids, test for, 44 

test for, in sahva, 210 

titration for, 101 

distinction from HBr and HI, 46 
Chlorin in teeth and tartar, 121 
Chlorin, test for, in organic sub- 
stances, 124 
Chlorochromic anhydrid, 22 

test for chlorids, 46 
Chloroform, 112, 129 

preparation, Exp. 10, 130 

test for, 112 
Cholahc acid, 223 
Cholesterin, 225 
Chondro-proteids, 191 
Chromates, test for, 47 
Chrome alum, 22 
Chromic-acid test, 4S 
Chromic anhydrids, CrOg, 22 
Chromite, 22 
Chromium oxids, 22 
Chromium salts, 22 
Chromous salts, 22 (note) 
Cinnabar, 4 
Citric acid, 144 
Cleaning of mercury, 87 
Closed-chain hydrocarbons, 161 
Closed-tube tests, 53 
Cloudy urine, 228 
CO haemoglobin, 194 
Coarse solder, 80 
Cobalt, 24 

salts, reactions of, 24, 25 

separation from nickel, 25 
Cocain, 112, 138 

composition of, 138 

microchemical test for, 112 
Coefficients of expansion, 62 
Coin silver, 64 
Collagen, 199 

Color-test for amalgam, 73 
Colors of salts, 51 
Common solder, 79 
Compound ethers, 135, 138 
Compound proteids, 183 
Conducti\'ity of metals, 62 
Congo-red, 94 
Conjugate sulphates, 167 
Contraction of amalgam, 73 
Copper, 6 

amalgam, 70 

blo^T)ipe test, 55 

cement, oxyphosphate, 77 

determined by electrolysis, 103 

effects of. in alloy, 72 

estimation of, 102 



INDEX. 



265 



Copper glance, G 

Copper, oxyphosphate of, 77 

Copper pyrites, 

Copperas, 20 

Corrosive sublimate, 115, 

tests for, 115 
Corrugated gold, 67 
Cream of tartar, 148 
Creatiu, 199 

preparation of, Exp. 125, 201 
Creatinin, 199 

preparation of, Exp. 120, 202 
Creosol, 113 
Creosote, 112 

and carbolic acid, to distinguish 
between, 112 
Crushing strength of amalgams, test, 

74 
Crj^olite, 34 
Crystals, formation of, 105 

from saliva, 212 

microchemistry, 106 
Cuprum, 6 
CuSO^ solution, 260 
Cyanic acid, 153 
Cyanids, test for, 43, 46 
Cyanogen compounds, 152 
Cyanuric acid, 154 

from uric acid, 157 
Cychc hydrocarbons, 161 
Cystin, 181 

preparation of, 253 

Decinormal factor, 91 
Decinormal solution, 91 
Defibrinated blood, 194 
Dental alloy, quantitative analysis 

of, 102 
Dental amalgam, 64 
Dental cements, 75 
Dental floss, testing contraction of, 

61 
Dental gold, 64 
Dental metallurgy, 59 
Dentine, composition of, 119 
Derived proteids, 182 
Dextrin, 174 
Dextrose, 171 
Diabetic sugar, 171 
Diacetic acid, 147, 243 
Dialyzed saliva, crystals from, 212 
Dialyzer for saliva, 212 
Diamins, defined, 149 
Dibasic acids, 145 
Dibasic amido acids, 149 
Digestion, 203 



Di-hydroxy-benzenes, 162 

I)i-hydroxy-succinic acid, 144 

Di-mcthyl-amido-azobenzol, 220 

Di-methylamin, 149 

Di-methyl benzene, 163 

Di-methyl ketone, 134 

Di-oxy-purin, 157 

Di-saccharids, 171 

Dolomite, 30 

Doremus's Urea Apparatus, 232 

Double-bonded hydrocarbons, 127, 

137 
Ductility of metals, 62 
Dysalbumose, 189 

Egg-albumin, 183 

Ektogan, 113 

Electric currents in the mouth, 63 

Eleopten, 177 

Emulsification, 177 

Exp. 70, 179 
Emulsifying agents, 177 
Enamel, artificial, 78 

composition of, 119 
End point defined, 90 
Enzymes, 169 
Epithelium in urinarv' sediments 

248 
Erythrodextrin, 173 
Esbach's albuminometer, 239 
Esbach's reagent, Exp. 82, 186 
Essence of checkerberrv', 165 
Essential oils, 116 
Esters, 138 
Ethan, 125 
Ether, 136 

definition of, 135 

preparation, Exp. 17, 142 
Ethereal sulphates, 167 
Ethers, 135 
Ethyl-acetate, 138 
Ethyl-alcohol, 131 
Ethvl-bromid, 128 
Ethvl-but>^rate, 138 
EthVl-chlorid, 113, 128 
Ethvl-ether, 136 
Ethyl-nitrate, 136 
Ethyl-nitrite. 139 
Ethyl-oxid, 136 
Ethyl-sulphate, 136 137, 
Ethyl-sulphuric acid, 137 
Ethylene, 137 

chlorid, 127 

series, 127 
Ethvlidene lactic acid, 146 
Eucain, 113 



266 



INDEX. 



Eucain lactate, 113 
Euzone, 115 

Excess of mercury in amalgam, 72 
Expansion and contraction of amal- 
gam, test, 73 
Expansion, coefficients of, 62 

of amalgams, 73 

of metals, 63 

of plaster, 59, 60 
Experiments 

with albumin and globulin, 186 

with albumose and peptone, 189 

with alcohols, aldehyds, and 
ethers, 141 

with aromatic hydrocarbons, 167 

with bile, 224 

with blood and bone, 196 

with carbohydrates, 175 

with cyanogen compounds and 
urea, 159 

with fats and oils, 178 

with hydrocarbons, 129 

with keratin, 200 

with milk and mucins, 192 

with muscle and keratin, 200 

with organic acids, 150 

with pancreatic juice, 223 

Fat, wax, etc., on platinum, 52 
Fats, 139 

and oils, 177 

and oils, emulsification, 179 

composition of, 139, 140 

in urinaiy sediments, 250 

saponification of, 178 
Fatty acids, 143 
Fehling's solution, preparation of, 

258 
Fehling's test for sugar (Exp. 54), 175 
Fermentation test for sugar (Exp. 

58), 176 
Ferments, 169 

Ferri et ammonii tartras, 148 
Ferri et potassii tartras, 148 
Ferrocyanids, test for, 46 
Fibrin, 194 

experimental digestion, 219 
Fibrinogen, 194 

Filtration in microchemistry, 106 
Fine solder, 80 
Five-drop test for saliva, 210 
Flagg's submarine alloy, 73 
Flame test, 54 

Fleitmann's test for arsenic, 11 
Fletcher's gold alloy, 73 
Flow of amalgams, 68 



Flux for aluminum solder, 80 
Formal, 113 
Formaldehyd, 113 

preparation of (Exp, 13), 141 

test for (Exp. 14), 141 
Formaline, 113 

test for (Exp. 14), 141 
Formic acid, 144 

preparation of (Exp. 23), 151 
Formic ether, 136 
Formine, 113 
Formol, ll3 
French chalk, 30 
Freiid and Topfer test for urinary 

acidities, 230 
Frohde's reagent, 116 
Fulminates, 153 
Fulminic acid, 153 
Fusel oil, 131 
Fusible metal, 85 

for crown and bridge-work. Dr. 
Richmond, 86 

Gad's experiment, 179 

Galena, 4 

Galvanic properties of metals, 63 

Gastric contents, analysis of, 218 

Gastric digestion, 217 

Gelactose, 171, 172 

Gelatine, 196 

preparation of, 198 
German silver, 64 
Glacial acetic acid, 145 
Globuhn, 184 

experiments with, 187 

precipitation by dialysis, 187 

precipitation by magnesium sul- 
phate, 187 
Glucose, 171 
Glue, 196 
Glycerine, 113, 131, 140 (Glycerol) 

test for, 113 
Glycerol, 140 
Gly eery 1-buty rate, 139 
Glyceryl-oleate, 139 
Glyceryl-palminate, 139 
Glyceryl-stearate, 139 
Glycin, 148 

Glycochohc acid, 222, 223 
Glycocoll, 148 
Glycogen, 174 

in muscle, 200 

test for, in sahva, 211 
Glyco-proteids, 191 
Gmelin's test for bile pigments (Exp. 
155), 225 



INDEX. 



26: 



Gold, 15 

alloys, 82 

aluminum solder, 80 

amalgams, 70 

and silver, dry assay of, 104 

annealing of, 67 

corrugated, 67 

dry assay of, 104 

effect of, in alloy, 72 

estimation of, 103 

non-cohesive, 67 

recovery of, 86 

salts, reactions of, 15 

salts, volumetric determination of, 
100 

solder, 81 
Grain alcohol, 131 
Grape sugar, 171 
Group 1, analysis of, 5 
Group II (a), analysis of, 17 
Group II (6), analysis of, 18 
Group III, analysis of, 22 
Group IV, analysis of, 27 
Group V, analysis of, 31 
Group I, reactions of, 3 
Group II, reactions of, 6 
Group III, reactions of, 20 
Group IV, reactions of, 24 
Group V, reactions of, 29 
Group VI, reactions of, 33 
Group reagents, 2 
Guaiacol, 162 
Guanin, 157 
Guncotton, 175 
Gunsburg's reagent, 220 
Gutzeit's test for arsenic, 10 
Gypsima, 30, 59 

Hsematin, 194 
Htemin, 195 

crystals, preparation of (Exp. 

115), 197 
Hiemochromogen, 194 
Hsemoglobin crystals (Exp. 113), 

test for, 194, 196 
Hair, keratin in, 200 
Halogens in organic substances, 124 
Hard soap, 140 
Harris' amalgam alloy, 73 
Hea\y spar, 29 
Hematoporphyrin, 228 
Hemipeptone, 184 
Hemostatin, 109 
Heroin, 114 

Heterocyclic compounds, 166 
Heteroxanthin, 157 



HgClj solution, 260 
High-grade alloy, 73 
Hippuric acid, 165 
Histidin, 182 

Homocyclic, definition, 166 
Homologous series, 125 
Homologues, definition, 125 
Hopogan, 114 
Horismascope, 238 
Hydrargyrum, 4 
Hydrazines, 150 
Hydrocarbons, 124 

definition of, 122 
Hydrochloric acid in the stomach. 

217 
Hydrochloric acid, standard solution, 

95 
Hydrochloric acid, test for free, : 20 
Hydrocyanic acid, 152 

preparation of, 159 
Hydrogen dioxid, 114 
Hydrogen equivalent, 89 
Hydrogen peroxid, 114 

assay of, 98 

titration of, 98, 99 
Hydrogen, test for, in organic matter, 

123 
Hydrolysis, 170 

Hydrolytice nzyme, definition of, 170 
Hydroquinone, 162 
Hypoacid sahva, appearance of, 211 
Hypochlorites, test for, 45 
Hypoxanthin, 157, 200 

Ignition on platinum foil, 52 

Incisors, tartar of, 119 

Indicators, 93 

Indol, 167 

Indoxyl, 167 

Indoxyl-potassium sulphate, 167 

Inosite, 200 

lodids and bromids, separation of, 46 

lodids with AgNOg, 44, 46 

lodids with HCl and HBr, 46 

lodin closed-tube test, 54 

Iqdin decinormal solution, 98 

lodin on platinum, 53 

lodin test for bile, 225 

lodin test for, in organic substances, 

124 
Iodoform (Exp. 11), 130 

production of (Exp. 11), 128 
Iron, 20 

blowpipe test, 55 
Iron, final tests for, 24 
Iron salts, reactions of, 20, 21 



268 



INDEX. 



Iron scale, salts of, 148 

Isobenzonitnl, 153 

Isobenzonitril, test for chloral, 142 

Isobutan, 126 

Isocyanic acid, 153 

Isocyanids, 152 

Isocyclic, definition of, 166 

Isomers, 126 

Isonitrils, 152 

Isopentan, 132 

Kalium, 33 

Keratin, 200 

Ketones, 134 

Ketose, 171 

K,Fe(CN)6 solution, 260 

King's Occidental alloy, 73 

Kingzett's method for determining 
H2O2 with thiosulphate solu- 
tion, 99 

Kjeldahl process for nitrogen, 123 

Lacmoid, 93 
Lactic acid, 146 

in muscle, 200 

test for, 220 

test (Exp. 22), 150 
Lactalbumin, 191 

Lactophosphate of lime and mag- 
nesium, 213 
Lactose, 173 
L3evulose, 172 
Lead, 4 

blowpipe test, 55, 56 

final tests for, 5 

in saliva, 216 

in urine, 244 
Lead salts, reaction, 5 
Lecithin in saliva, 210 
Legal's test for acetone, 243 
Leucin, composition of, 149 

formation of (Exp. 146), 223 

in sahva, 210 

isolation of, 258 
Leucocytes, 195 
Limestone, 30 
Lipase, 170 

Lipolytic enzymes, 170 
Lithium as uric-acid solvent, 158 
Lithium, salts of, reactions, 35 
Litmus, 93 
Local anaesthetics, 108 

Magnesite, 30 

Magnesium blowpipe test, 56 

Magnesium mixture, 258 



Magnesium salts, 30 

reactions of, 30 
Magnesium, test for, in teeth, 121 
Magnesium - ammonium - phosphiite, 

108 
Malchite blue, 6 
Malchite green, 6 
Malic acid, 144 

test for (Exp. 27), 151 
Malleability of metals, 62 
Malonic acid, 144 
Maltase, 207 
Maltodextrin, 173 
Maltose, 173 
Manganese dioxid, 25 
Manganese, red lead, test for, 25 

salts, reactions of, 25 

separation from zinc, 28 
Mannite, 131 
Marble, 30 
Marsh gas, 124, 129 
Marsh-Berzelius test for arsenic, 11 
Marsh's test for arsenic, 13 
Matrass, 10 

Measuring instruments, 92 
Meconic acid, distinction from HCyS 

(Exp. 131), 215 
Meerschaum, 30 
Mellot's metal, 85 
Melting-point of metals, 62 
Menthol, 115, 177 
Mercuric chlorid, 115 

closed-tube test, 54 

microchemical test for, 115 

test, 115 
Mercuric salts, test, 115 
Mercurous chlorid, closed-tube test, 

54 
Mercurous salts, 4 

reactions, 7 
Mercury, 4 

cleaning of, 87 

detection, in saliva, 216 

excess of, in amalgam, 72 

in saliva, 276 

physical tests for pure, 88 

recovery of, 87 
Metaloids, 1 
Metals, 1 

conductivity of, 62 

ductility of, 62 

extraction from ore, 61 

melting-point of, 62 

occurrence of, 59 

properties of, 62 
Metaphosphate cement, 75 



INDEX 



2G9 



Metastannic acid, 14 
Methan, 125 
Methethyl, 115 
iMothyl-alcohol, 131 
Methylainin, 149 
Methyl-beiizeno, 163 
Methyl-carhamine, 152 
Methyl-carbinol, 131 
Methyl-chlorid, 115 
Methyl-clilorolonn, 129 
Mcthyl-cyanid, 152 
Methyl-etlicr, 136 
Methyl-ethyl-cther, 136 
Methyl-indol, 167 
Methyl-iodid, 128 
Methyl-isopropyl carbinol, 132 
Methyl-orange, 93 
Methyl-oxid, 136 
Methyl-salicylate, 138 
Methyl-urea, 155 
Methylene chlorid, 128 
Methylene ether, 136 
Methyl-ethyl-ether, 136 
Microchemical analysis, 105 
Milk, cow's, composition of, 191 

cows' and human, compared, 191 

human, composition of, 191 
Modified milk, 191 

Mohr's method for titration of ar- 
senic, 99 
Molars, tartar of, 119 
Molish's test for carbohydrates (Exp. 

51), 175 
Monochlormethan, 113 
Monosaccharids, 171 
Morphine, 116 

microchemical test for, 116 

separation of, 116 
Mucin, in saliva, 206, 213 

in urine, 250 

preparation of, 256 
Mucins, 191 
Mucoids, 191 
Murexid, 158 

test, uric acid (Exp. 39), 160 
Muscle, 199 
Muscle plasma, 199 
Muscle serum, 199 
Musculin, 201 
Myogen, 201 
Mvogenfibrin, 201 
Myosin, 199, 201 
Myosinogen, 199 

Nails, ke -atin in, 200 
NaOH solution, 259 



Natrium, 34 

Nessler's reagent, preparation of, 259 
Neucloo-protoids and definition, 190 
Nickel, salts of, 25 

separation of, from cobalt, 25 
Nitrates, solubility of, 41 

test for, 49 
Nitrils, 152 
Nitrites, test for, 45 
Nitroi)enzene, 1(53 

preparation of (Exp. 44), 168 
Nitrogen, test for, 123 
Nitroglycerin, 116 
Noble nietai, 1 
Non-cohesive gold, 67 
Normal factor, definition, 89 
Normal solution, definition, 89 
N/10 factor, 91 
N/10 solution, 91 

Oil of betula, 138 

of bitter almonds, 164 

of clove, 116 

of gaulthcria, 138 

of mirbane, 163 

of wintergreen, 138 
Oleic acid, 145 
Organic acids, 143 
Organic chemistry, 122 
Organized ferments, 169 
Orpiment, 9 
Orthoform, 116 

Orthohydroxy-benzoic acid, 164 
Osazones, 172 
Ossein, 196 
Outline of analysis: 

Group I, 38 

Group II, 38 

Groups III and IV, 39 
Oxalates in the system, 146 
Oxalates test, 44, 49 
Oxahc acid, 145 

closed-tube test, 54 

in vegetables and fruit, 146 

on platinum, 52 

standard solution, 94 

test for, 47 
Oxaluric acid, 155 
Oxid of zinc, to make pure, 76 
Oxidation and reduction, analysis 

by, 96 
Oxy-acids, 146 

defined, 147 
Oxy-benzene, 163 
Oxy-benzoic acid, 164 
fi Oxy-butyric acid, 147 



270 



INDEX. 



Oxy-chlorid of zinc cement, 77 
Oxy-haemoglobin, 194 
Oxy-phosphate of copper, 77 
Oxy-phosphate of zinc cement, 75 
Oxy-sulphate of zinc, 77 

Pancreatic digestion, 222 

Parabanic acid, 156 

Paraform, 126 

Paraglobulin, 187 

Paralactic acid, 147 

Paraldehyd, 133 

Paramyosinogen, 201 

Paris green, closed-tube test, 54 

Pentan, 125 

Pepsin, 217 

Pepsin-hydrochloric acid, 218 

Peptones, 189 

Permanganate of potash, standard 

solution, 96 
Permanganate of potash, titration 

with oxalic acid, 97 
Peroxid of hydrogen, titration with 

permanganate, 98 
Peroxid of hydrogen, titration with 

thiosulphate, 99 
Peroxid of zinc, 113 
Phenol, 163 

test for, 111 
Phenol-disulphonic acid, 163 
Phenol-sulphonic acid, 163 
Phenolphthalein, 93 
Phenyl-hydrazine, 150 

solution, 258 

test for sugar, 176 
Phenyl-isocyanid, 134 
Phenyl-salicylate, 165 
Phenyl-sulphuric acid, 164 
Phloroglucin, 164 
Phosphates, in saliva, 209 

in urinary sediment, 247 

in urine, 234 

test for, 44, 48 

quantitative determination of, 235 
Phosphoric acid, test for, in teeth, 120 

to make pure, 76 
Phosphorous, test for, in organic 

matter, 124 
Physiological chemistry, 169 
Picric acid, 164 

solution (Esbach's reagent), 239, 
259 
Pineapple essence, 138 
Piotrowski's test, 185 
Plaster of Paris, 59 

expansion of, 59, 60 



Plaster-of-Paris mixture, 61 
Platinum, 16 

anneahng of, 67 

effect of, in alloys, 72 

solder for, 83 
Platinum aluminum solder, 81 
Platinum amalgam, 70 
Platinum salts, reactions of, 16 
Plumbum, 4 
Polymers, 126 
Polysaccharids, 171 
Potassium, 33 

Potassium-acid tartrate, 148 
Potassium aluminate, 21 
Potassium bitartrate, 148 
Potassium cyanate, preparation of 

255 
Potassium hydroxid, 116 
Potassium platinic chlorid, 33 
Potassium salts, 33 
Potassium sulphocyanate, 208 
Potato spirit, 131 
Powder of algaroth, 13 
Prehminary examination of solids. 

51, 52 
Primary alcohol, 132 
Propan, 125 
Propenyl alcohol, 139 
Properties of the metals, 62 
Propylene, 127 
Proteids, 180 

classification of, 180 

color reactions for, 185 

general precipitants for, 185 

general reactions of, 184 
Protein, 180 

Proteolytic enzyme, definition, 170 
Proteoses, 188 

Piotrowski's test (Exp. 74), 185 
Prussian blue, 21 
Prussic acid, 152 
Pseudo-nucleo albumin, 183, 190 
Ptomains, 150 
Ptyalin, 207 

activity of, 213, 214 

conditions influencing action of 
214 
Purin, 156 
Purple of Cassius, 15 
Pus, definition, 195 
Putrescin, 150 
Pyorrhoea, tartar from, 119 
Pyridin, 166 
Pyro-catechin, 162 
Pyrolusite, 25 
Pyrotartaric acid, 149 



INDEX. 



271 



Questions on group I, G 

on group 11, 19 

on group 111, 24 

on group IV, 28 

on group V, 33 
Quinalin, IGG 

Reactions of group 1, 3 

of group II, () 

of group 1X1, 20 

of group IV, 24: 

of group V, 29 

of group VI, 33 
Reaction of urine, 229 
Realgar, 9 

Recovery of scrap, 86 
Red-lead test for manganese, 2.5 
Red litmus-paper (note), 35 
Red precipitate, 8 
Reinsch's test for arsenic, 10 
Renal casts, 249 
Rennin, 218 
Residue, recovery of gold, 86 

recovery of mercury, 87 

recovery of silver, 87 
Resorcin. 162 
Rhigolene, 116 

Richard's solder for aluminum, 80 
Rochelle salts, 148 
Rose's metal 85 

Rule to change carat of alloys, 84 
Rule to determine carat of alloys, 84 

Sahcylic acid, 164 
Saliva, 203 

abnormal constitents, 206 

color, 205 

normal constitents, 205 

odor, 205 

physical properties of, 204 

quantity, 204 

reaction, 204 

specific gravity, 204 
Salol. 165 

Salts and solutions, color of, 51 
Saponification, 140, (Exp. 67) 178 
Sarsapariila, need for, 159 
Saturated hydrocarbons, 127 
Scale salts of iron, 148 
Secondary alcohols, 131, 132 

oxidation of, 134 
Selenium, blowpipe test, 56 
Serum albumin, 183 
Serum, blood, 193 
Setting of amalgams, 67 
Silica bead test. 47 



Silicates, blowpipe test, 56 

Silicic acid, test for. 47 

Silver, decincjrmal solution of, 101 

dry assay of, 104 

effect of, in amalgam, 71 

recovery of, 87 
Silver albuminate, 51 
Silver amalgam, 70 
Silver arsenide, 1 1 
Silver blowpipe test, 55 
Silver glance, 3 

Silver nitrate, N/10 solution, 101 
Silver nitrate solution for urine, 101 
SiKer salts, reaction, 3 
Silver solder, 85 
Simple ethers, definition of, 135 
Simple proteids, 182 
Skatol, 167 
Skatoxyl, 167 

potassium sulphate, 167 
Smithsonite, 26 
Soaps, 140 
Soapstone, 30 
Sodium amalgam, 69 
Sodium chlorid, decinormal solution, 
101 

in anaesthetics, 117 
Sodium oxalate, microchemical for- 
mation of, 107 
Sodium perborate, 115, 117 
Sodium peroxid, 114 
Sodium phosphate with uric acid, 158 
Sodium pyroantimonate, 34 
Sodium salts, 34 
Sodium tetraborate, 110 
Sodium thiosulphate, decinormal so- 
lution, 98 
Sodium zincate, 26 
Soft soap, 140 
Soldering acid, 80 
Solders, for aluminum, 80 

for brass, 81 

for gold, 81 

for platinum, 83 

for silver, 85 
Soft solders, 80 
Solids, total, in saliva, 212 
Solubihty of salts, 41 
Soluble cotton, 175 
Soluble starch, 173 
Somnoform, 117 
Specific gravity, of amalgams, 74 

of saliva, 211 

of urine, 229 
Spermatozoa, 250 
Spiritus etheris nitrosi, 130 



272 



INDEX. 



Squibb's urea apparatus, 231 
Standard dental alloy, 73 
Standard solutions, defined, 90 

preparation of, 90 
Stannum, 14 
Starch, 173 

Starch paste (Exp. 63), 176 
Steapsin, 222 
Stearopten, 177 
Sterling silver^ 64 
Stibium, 13 
Stibnite, 13 

Stokes' reagent (note), 197 
Stomach steapsin, 218 
Straight-chain hydrocarbons, 126 
Stroma, 194 
Strontianite, 29 
Strontium oxalate, 29 

micro-chemical formation, 107 
Strontium salts, 29 
Sublimates, various, 54 
Substituted ammonias, 149 
Substituted ureas, 155 
Substitution products, 125 
Succinic acid, 146 
Sugar in saliva, 209 
Sugar, quantitative determination 

of, 241 • 
Sulphates, in urine, 236 

test for, 44, 47 
Sulphids, test for, 43, 44, 45 
Sulphites, test for, 43 
Sulphocyanates of potassium, 208 

test for, 46 

test for, in saliva, 210 
Sulphocyanic acid, 153 

test for, 46, 210 
Sulphur, closed-tube test, 54 
Sulphur iodid, for blowpipe work, 55 
Sulphur on platinum, 52 
Sulphur, test for in organic matter, 

124 
Sulphuric acid, standard solution, 95 
Supraredalin, 109 
Sweet spirits of nitre, 139 
Sylvite, 33 

Symmetrical hydrocarbons, 162 
Symmetrical substitution products, 
162 



Table of solubilities. 
Talcum, 30 
Tannic acid, 118 



41 



118 



Tartar, composition of, 1 19 
from pyorrhoea, 119 



Tartar of incisors, 119 

of molars, 119 
Tartar emetic, 13, 148 
Tartaric acid, 144, 148 
Taurocholic acid, 222 
Teeth, composition of, 119 
Teeth and tartar, 118 

analysis of, 120 
Teichmann's hsemin test, 197 
Temporary alloy, 73 
Tertiary alcohols, 132 
Tests for amalgam, 73 
Thein, 157 
Thio-cyanates, 46 
Thio-cyanic acid, 153 
Thio-sulphates, 43 
Thrombase, 193 
Thrombin, 193 
Thymol, 177 

test for, 118 
Tin, 14 

action of HNO3, 14 

amalgam, 70 

cement, 77 

estimation of, 103 
Tin salts, reactions of, 14 
Tinstone, 14 
Titration defined, 95 
Tollen's test for aldehyd (Exp. 16), 

142 
Toluene, 163 

Total solids in saliva, 212 
Tribrommethan, 129 
Tribromphenol (Exp. 45), 168 
Trichloracetic acid, 118 
Trichloraldehyd, 111 
Trichlormethan, 129, 112 

test for, 112 
Trihydroxybenzene, 164 
Tri-iodomethan, 128 
Trimethylamin, 149 
Trinitrocellulose, 175 
Trinitrophenol, 164 
Triolein, 139 
Trioxypurin, 157 
Tripalmitin, 139 

melting-point, 140 
Tristearin, 139 

melting-point, 140 
Triple phosphate, 247 
Tritenyl, 139 
Tropa-cocain, 118 
Trypsin, 222 
Type-metal, 64 
Ty rosin, 165 

formation of (Exp. 146), 223 



INDEX. 



273 



Tyrosin, isolation of, 257 

I'ffelmann's reagent, 220 

Unorganized ferments, 169 

Unsaturated hydrocarbons, 127 

Unsynimetrical hydrocarbons, 162 

Unsymmetrical substitution prod- 
ucts, 162 

Uranyl and sodium acetate, 34 

Urates in urinary sediment, 247 

Urea, 153, 230 
in saliva, 209 
nitrate, ioo 
oxalate, 155 
oxalate, microchemical formation 

of, 108 
quantitative determination of, 231 
reaction with hypobromite, 154 
Squibb's apparatus for, 231 
synthesis of (Exp. 34), 159 

Urease, 170 

Ureids, defined, 155 

Uric acid, 156 

in urinary sediments, 246 

in urine, 232 

murexid test for (Exp. 39), 160 

quantitative determination of, 233 

with NagHPO, in the blood, 158 

Urinary sediments, 245 

Urine, 226 

chlorids in, 233 
collection of samples, 227 
method of clearing cloudy, 228 
normal constituents of, 230 
phosphates in, 234 
physical properties of, 227 
quantity, color, and appearance of, 

227, 228 
reaction, 229 
solids by calculation, 230 
specific gravity, 229 
to filter cloudy samples, 228 



Urinometers, 229 
Urinopyknometer, 229 
Urophain, 236 

Vinegar, titration of, 96 
Vitriol, white, 26 
Volatile alkali, 35 
Volumetric analysis, 89 

White arsenic, 9 

closed-tube test, 54 
White precipitate, 8 
White vitriol, 26 

Will and Varrentrap's test for nitro- 
gen, 123 
Witherite, 29 

Xanthin, 157 

Xanthoproteic test (ILxp. 72), 185 

Xylene, 163 

Yellow wash, 7 

Zinc, 26 

blowpipe test, 56 

effect of, in alloys, 71 

estimation of, 103 

separation from manganese, 28 
Zinc amalgam, 70 
■ Zinc blend, 26 
Zinc-gold solder, 81 
Zinc oxalate, 27 
Zinc oxid, closed-tube test, 54 

to make pure, 76 
Zinc oxychlorid, 77 
Zinc oxyphosphate, 75 
Zinc oxysulphate, 77 
Zinc peroxid, 113, 114 
Zinc salts, reaction, 26, 27 
Zymase, 170 
Zymogen, 169 



PLATE I. 





Fi(i. 1. 
Ammonium rMatiiiic Chlorid. 



Fk;. 2. 
Zinc Oxjilatc. 




Fig. a. 
Strontium Oxalate. 




Fig. 4. 
Magnesium Ammonir.m Phosphate. 





Fig. o. 
Potassimn Platinic Chlorid. 



Fig. 6. 
I'ranvl Sodium Acetate. 



PLATE II 





Fk;. 1. 
Oxalic Acid (Suhliined). 



Fig. 2. 

Arsenic Trioxid. 





Fig. ;i. 
Mercuric Chlorid (Sublimed). 



Fig. 4. 
Aiiinionium Sidphate (Suhliniedj. 




Fig. 5. 
Mercury from HgO. 




PLATK HI. 




Vui. 1. 
Calcium Oxalate. 




Fig. 8. 
Sodium Oxalate (P. L.). 





Fic. 2. 
Cadmium Oxalate 




Fk;. 4. 
Oxalate of I'rea. 




Fig. 5. Fig. 6. 

Ammonium Phospho-molybdate. A, Sodium Urate; B, Sodium Acid Urate. 
No. 3 and No. 7 Leitz Objective. 



rLATJ^ IV. 




Fio. 1. 
Tri-brom-phonol. 




Fig. 3. 

Morphin and Marme's Reagent. 





Fig. 2. 
Morphin. 




Fig. 4. 
Chloretone and Sodiiun Hypochlorite. 




Fig. 5. 
Cocain and Potassium Permanganate. 



Fig. (3. 
Cocain with Tin Chlorid. 



PLA'ii-: y 




Fig. 1. 
Iodoform. 





Fig. 3. 
Urea Nitrate. 



Fig. 4. 
Hippuric Acid. 





Fig. 5. 
Uric Acid. 



Fig. (5. 
Uric Acid. 



PLATE VI. 





Fici. 2. 
Glucosozone. 




Fig. 3. 
Maltosazone. 



Fig. 4. 
Lactosazone. 





Fig. 5. — Fat Crystals. 
A, Butter Crystals; B, Lard Crystals. 



Fig. 6. 
A, Fat Acid; B, Cholesterin. 



PLATE VII. 



be 



B'^O 



<.■ o 


r, 


^ 


t 


' -% 


■ 


E. * 


B 


% 


;\ 




A 




lie;. 1. Fk;. 2. 

A, Corn starch; /^, Rice .starch. A Potato stan-h; />, Arrowroot starch. 





Fig. 3. 
Bean starch. 



Fig. 4. 
Wheat starch. 




Fig. 5. 
A, Human Blood; B, Horse Bl;)od; 
C, Dog Blood. 




Fig. 6. 
Fro- Blood; B, Chicken Blood. 
G, Fish Blood; 



PLATE VIII 




Fig. 1. 
Ammonium Chloric!. 




Fig. 3. 

A, Magnesimn Lactate (P. L.); 

B, Calcium Lactate (P. L.). 





Fig. 2. 
Teichmann's Hemin Crystals, 




Fig. 4. 

A, Mg. Lacto-phosphate (P. h.): 

B, Ca, Lacto-phosphate (P. L.). 



Fig. 5. 
Formaldehj'd Urea (P. L.). 




PL ATI:: IX. 




Fl(!. 1. 

Aniinoniuin Acid Frate. 




Fig. 3.— Pus. 
A, After addition of Acetic Acid 




Fig. 5. 
False Casts and ^lucin. 




Fig. 2. 
Spermatozoa. 




Fig. 4. 
Renal Casts. 




F^iG. G. 
A, Lycopodiiim; B, Moth-scales; C, Cork; 
D, Cotton-fibres; E, Wool-fibres. 



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Wilson's Cyanide Processes '. i2mo, i 50 

Chlorination Process i2mo, i 50 

Winton's Microscopy of Vegetable Foods Svo, 7 50 

Wulling's Elementary Course in Inorganic, Pharmaceutical, and Medical 

Chemistry i2mo, 2 oa 

5 



CIVIL ENGINEERING. 

BRIDGES AND ROOFS HYDRAULICS. MATERIALS OF ENGINEERING. 
RAILWAY ENGINEERING. 

Baker's Engineers' Surveying Instruments izmo, 

Bixby's Graphical Computing Table Paper 19^X24^ inches. 

** Burr's Ancient and Modern Engineering and the Isthmian Cana .. (Postage, 

27 cents additional.) 8vo, 

Comstock's Field Astronomy for Engineers 8vo, 

Davis's Elevation and Stadia Tables 8vo, 

Elliott's Engineering for Land Drainage i2mo, 

Practical Farm Drainage i2mo, 

*Fiebeger's Treatise on Civil Engineering Svo, 

Flemer's Phototopographic Methods and Instruments Svo, 

Folwell's Sewerage. (Designing and Maintenance.) Svo, 

Freitag's Architectural Engineering. 2d Edition, Rewritten Svo, 

French and Ives's Stereotomy Svo, 

Goodhue's Municipal Improvements i2mo, 

Goodrich's Economic Disposal of Towns' Refuse Svo, 

Gore's Elements of Geodesy Svo, 

Hayford's Text-book of Geodetic Astronomy Svo, 

Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 

Howe's Retaining Walls for Earth i2mo, 

Johnson's (J. B.) Theory and Practice of Surveying ; Small Svo, 

Johnson's (L. J.) Statics by Algebraic and Graphic Methods Svo, 

Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . i2mo, 
Mahan's Treatise on Civil Engineering. (1873.) (Wood.) Svo, 

* Descriptive Geometry Svo, 

Merriman's Elements of Precise Surveying and Geodesy Svo, 

Merriman and Brooks's Handbook for Surveyors i6mo, morocco, 

Nugent's Plane Surveying Svo, 

O^den's Sewer Design i2mo, 

Patton's Treatise on Civil Engineering Svo half leather. 

Reed's Topographical Drawing and Sketching 4to, 

Rideal's Sewage and the Bacterial Purification of Sewage Svo, 

Siebert and Biggin's Modern Stone-cutting and Masonry Svo, 

Smith's Manual of Topographical Drawing. (McMillan. "> Svo, 

Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 

Svo, 
Taylor and Thompson's Treatise on Concrete, Plain and Reinforced Svo, 

* Trautwine's Civil Engineer's Focket-book i6mo, morocco, 

V/ait's Engineering and Archi ectural Jurisprudence Svo, 

Sheep, 
Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture Svo, 

Sheep, 

Law of Contracts Svo, 

Warren's Stereotomy — Problems in Stone-cutting Svo, 

Webb's Problems in the Use and Adjustment of Engineering Instruments. 

i6mo, morocco, 

Wilson's Topographic Surveying Svo, 



BRIDGES /ND ROOFS. 

Boiler's Practical Treatise on the Construction of Iron Highway Bridges. .Svo, 2 00 

* Thames River Bridge 4to, paper, 5 00 

Burr's Course on the Stresses in Bridges and Roof Trusses, Arched Ribs, and 

Suspension Bridges Svo, 3 50 

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Burr and Falk's Influence Lines for Bridge and Roof Computations. . . .8vo, 

Design and Construction of Metallic Bridges 8vo, 

Du Bois's Mechanics of Engineering. Vol. II Small 4to, 

Foster's Treatise on Wooden Trestle Bridges 4to, 

Fowler's Ordinary Foundations 8vo, 

Greene's Roof Trusses Svo, 

Bridge Trusses Svo, 

Arches in Wood, Iron, and Stone Svo, 

Howe's Treatise on Arches Svo, 

Design of Simple Roof-trusses in Wood and Steel Svo, 

Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of 

Modern Framed Structures Small 4to, lo oo 

Merriman and Jacoby's Text-book on Roofs and Bridges: 

Part I. Stresses in Simple Trusses Svo, 2 50 

Part II. Graphic Statics Svo, 2 so 

Part III. Bridge Design Svo, 2 so 

Part IV. Higher Structures Svo, 2 50 

Morison's Memphis Bridge 4to, 10 00 

Waddell's De Pontibus, a Pocket-book for Bridge Engineers. . i6mo, morocco, 2 00 

*Specifications for Steel Bridges i2mo, so 

Wright's Designing of Draw-spans. Two parts in one volume Svo, 3 50 



HYDRAULICS. 

Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from 

an Orifice. (Trautwine.) Svo, 2 00 

Bovey's Treatise on Hydraulics Svo, 5 00 

Church's Mechanics of Engineering Svo, 6 00 

Diagrams of Mean Velocity of Water in Open Channels paper, i 50 

Hydraulic Motors Svo, 2 00 

Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, 2 50 

Flather's Dynamometers, and the Measurement of Power i2mo, 3 00 

Folwell's Water-supply Engineering Svo, 4 00 

Frizell's Water-power Svo, 5 00 

Fuertes's Water and Public Health i2mo, i 50 

Water-filtration Works i2mo, 2 50 

Ganguillet and Kutter's General Formula for the Uniform Flow of Water in 

Rivers and Other Channels. (Hering and Trautwine.) Svo, 4 00 

Hazen's Filtration of Public Water-supply Svo, 3 00 

Hazlehurst's Towers and Tanks for Water-works Svo, 2 50 

Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal 

Conduits Svo, 2 00 

Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 

Svo, 4 00 

Merriman's Treatise on Hydraulics Svo, 5 00 

* Michie's Elements of Analytical Mechanics Svo, 4 00 

Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- 
supply Large Svo, 5 00 

** Thomas and Watt's Improvement of Rivers. (Post., 44c. additionaL).4to, 6 00 

Turneaure and Russell's Public Water-supplies Svo, 5 00 

Wegmann's Design and Construction of Da^Js 4to, 5 00 

Water-supply of the City of New York from 1658 to 1895 4to, 10 00 

Williams and Hazen's Hydraulic Tables Svo, i 50 

Wilson's Irrigation Engineering Small Svo, 4 00 

Wolff's Windmill as a Prime Mover Svo, 3 00 

Wood's Turbines Svo, 2 50 

Elements of Analytical Mechanics Svo, 3 00 

7 



MATERIALS OF ENGINEERING. 

Baker's Treatise on Masonry Construction 8vo, 

Roads and Pavements 8vo, 

Black's United States Public Works Oblong 4to, 

* Bovey's Strength of Materials and Theory of Structiires 8vo, 

Biirr's Elasticity and Resistance of the Materials of Engineering Svo, 

Byrne's Highway Construction Svo, 

Inspection of the Materials and Workmanship Employed in Construction. 

i6mo, 

Church's Mechanics of Engineering Svo, 

Du Bois's Mechanics of Engineering. Vol. I Small 4to, 

♦Eckel's Cements, Limes, and Plasters Svo, 

Johnson's Materials of Construction Large Svo, 

Fowler's Ordinary Foundations Svo, 

* Greene's Structural Mechanics Svo, 

Keep's Cast Iron Svo, 

Lanza's AppUed Mechanics Svo, 

Marten's Handbook on Testing Materials. (Henning.) 2 vols .Svo, 

Maurer's Technical Mechanics Svo, 

Merrill's Stones for Building and Decoration Svo, 

Merriman's Mechanics of Materials Svo, 

Strength of Materials i2mo, 

Metcalf' s Steel. A Manual for Steel-users i2mo, 

Patton's Practical Treatise on Foundations Svo, 

Richardson's Modern Asphalt Pavements Svo, 

Richey's Handbook for Superintendents of Construction i6mo, mor., 

Rockwell's Roads and Pavements in France i2mo, 

Sabin's Industrial and Artistic Technology of Paints and Varnish Svo, 

Smith's Materials of Machines i2mo. 

Snow's Principal Species of Wood Svo, 

Spalding's H3'draulic Cement .... i2mo. 

Text-book on Roads and Pavements i2mo, 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced Svo, 

Thurston's Materials of Engineering. 3 Parts Svo, 

Part I. Non-metallic Materials of Engineering and Metallurgy Svo, 

Part II. Iron and Steel Svo, 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents Svo, 

Thurston's Text-book of the Materials of Construction Svo, 

Tillson's Street Pavements and Paving. Materials Svo, 

Waddell's De Pontibus. (A P«cket-book for Bridge Engineers.). . i6mo, m®r.. 

Specifications for Steel Bridges 12m©, 

Wood's (De V.) Treatise oa the Resistance of Materials, and an Appendix on 

the Preservation of Timber Svo, 

Wood's (De V.) Elements of Analytical Mechanics Svo, 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel . Svo, 4 00 



RAILWAY ENGINEERING. 

Andrew's Handbook for Street Railway Engineers 3x5 inches, morocco, 

Berg's Buildings and Structures of American Railroads 4to, 

Brook's Handbook of Street Railroad Location i6mo, morocco, 

Butt's Civil Engineer's Field-book i6mo, morocco, 

Crandall's Transition Curve i6mo, morocco, 

Railway and Other Earthwork Tables Svo, 

Dawson's "Engineering" and Electric Traction Pocket-book. . i6mo, morocco, 

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Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 00 

* Drinker's Tunnelling, Explosive Compounds, and Rock Drills. 4to, half mor., 25 00 

Fisher's Table of Cubic Yards Cardboard, 25 

Godwin's Raitoad Engineers' Field-book and Explorers' Guide. . . i6mo, mor., 2 50 

Howard's Transition Curve Field-book i6mo, morocco, i 50 

Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- 
bankments 8vo, I 00 

Molitor and Beard's Manual for Resident Engineers i6mo, i 00 

Nagle's Field Manual for Railroad Engineers i6mo, morocco, 3 00 

Philbrick's Field Manual for Engineers i6mo, morocco, 3 00 

Searles's Field Engineering i6mo, morocco, 3 00 

Railroad Spiral i6mo, merocco, i 50 

Taylor's Prismoidal Formulae and Earthwork Svo, i SO 

* Trautwine's Method of Calculating the Cube Contents of Excavations and 

Embankments by the Aid of Diagrams Svo, 2 00 

The Field Practice of Laying Out Circular Curves for Railroads. 

i2mo, morocco, 2 50 

Cross-section Sheet Paper, 25 

Webb's Railroad Construction i6mo, morocco, 5 00 

Wellington's Economic Theory of the Location of Railways Small Svo, 5 00 



DRAWING. 

Barr's Kinematics of Machinery Svo, 2 50 

* Bartlett's Mechanical Drawing Svo, 3 00 

* " " " Ab-ridged Ed Svo, i 50 

Coolidge's Manual of Drawing Svo, paper i 00 

Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- 
neers Oblong 4to, 2 50 

Durley's Kinematics of Machines Svo, 4 00 

Emch's Introduction to Projective Geometry and its Applications Svo, 2 50 

Hill's Text-book on Shades and Shadows, and Perspective Svo, 2 00 

Jamison's Elements of Mechanical Drawing Svo, 2 50 

Advanced Mechanical Drawing 8vo, 2 00 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, i 50 

Part n. Form, Strength, and Proportions of Parts Svo, 3 00 

MacCord's Elements of Descriptive Geometry 8vo, 3 00 

Kinematics; or. Practical Mechanism 8vo, 5 00 

Mechanical Drawing 4to, 4 00 

Velosity Diagrams 8vo, i 50 

MacLeod's Descriptive Geometry Small Svo, i 50 

* Mahan's Descriptive Geometry and Stone-cutting Svo, i 50 

Industrial Drawing. (Thompson.) 8vo, 3 50 

Moyer's Descriptive Geometry 8vo, 2 00 

Reed's Topographical Drawing and Sketching 4to, 5 00 

Reid's Course in Mechanical Drawing 8vo, 2 00 

Text-book »f Mechanical Drawing and Elementary Machine Design. Svo, 3 00 

Robinson's Principles of Mechanism 8vo, 3 00 

Schwamb and Merrill's Elements of Mechanism 8vo, 3 00 

Smith's (R. S.) Manual of Topographical Drawing. (McMillan.) Svo, 2 50 

Smith (A. W.) and Marx's Machine Design 8vo, 3 00 

Warren's Elements of Plane and Solid Free-hand Geometrical Drawing. i2mo, i 00 

Drafting Instruments and Operations i2mo, i 25 

Manual of Elementary Projection Drawing i2mo, i 50 

Manual of Elementary Problems in the Linear Perspective of Form and 

Shadow i2mo, i 00 

Plane Problems in Elementary Geometry i2mo, i 25 

9 



Warren's Primary Geometry i2mo, 75 

Elements of Descriptive Geometry, Shadows, and Perspective 8vo, 3 50 

General Problems of Shades and Shadows 8vo, 3 00 

Elements of Machine Construction and Drawing 8vo, 7 50 

Problems, Theorems, and Examples in Descriptive Geometry 8vo, 2 50 

Weisbach's Kinematics 'and Power of Transmission. (Hermann and 

Klein.) 8vo, 5 Oq 

Whelpley's Practical Instruction in the Art of Letter Engraving i2mo, 2 00 

"Wilson's (H. M.) Topographic Surveying 8vo, 3 50 

Wilson's (V. T.) Free-hand Perspective 8vo, 2 50 

Wilson's (V. T.) Free-hand Lettering 8vo, i 00 

Woolf's Elementary Course in Descriptive Geometry Large 8vo, 3 00 

ELECTRICITY AND PHYSICS. 

Anthony and Brackett's Text-book of Physics. (Magie.) Small 8vo, 

Anthony's Lecture-notes on the Theory of Electrical Measurements. . . . i2mo, 
Benjamin's History of Electricity '. 8vo, 

Voltaic Cell , 8vo, 

Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.).8vo, 

Crehore and Squier's Polarizing Photo-chronograph 8vo, 

Dawson's "Engineering" and Electric Traction Pocket-book. i6mo, morocco, 
Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von 

Ende.) i2mo, 

Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 

Flather's Dynamometers, and the Measurement of Power i2mo, 

Gilbert's De Magnete. (Mottelay.) 8vo, 

Hanchett's Alternating Currents Explained i2mo, 

Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 

Holman's Precision of Measurements 8vo, 

Telescopic Mirror-scale Method, Adjustments, and Tests. . . .Large 8vo, 

Xinzbrunner's Testing of Continuous-current Machines 8vo, 

Landauer's Spectrum Analysis. (Tingle.) 8vo, 

Le Chatelier s High-temperature Measurements. (Boudouard — Burgess.) i2mo. 
Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo, 

* Lyons' J Treatise on Electromagnetic Phenomena. Vols. I. and II. 8vo, each, 

* Michie's Elements of Wave Motion Relating to Sound and Light. 8vo, 

Niaudet's Elementary Treatise on Electric Batteries. (Fishback.) i2mo, 

* Rosenberg's Electrical Engineering. (Haldane Gee — Kinzbrunner.). . .8vo, 

Ryan, Norris, and Hoxie's Electrical Machinery. Vol. I 8vo, 

Thurston's Stationary Steam-engines 8vo, 

* Tillman's Elementary Lessons in Heat 8vo, 

Tory and Pitcher's Manual of Laboratory Physics Small 8vo, 

Ulke's Modern Electrolytic Copper Refining 8vo, 

LAW. 

* Davis's Elements of Law 8vo, 

* Treatise on the MiUtary Law of United States 8vo, 

* Sheep, 

Manual for Courts-martial i6mo, morocco, 

Wait's Engineering and Architectural Jurisprudence 8vo, 

Sheep, 
Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture 8vo. 

Sheep. 

Law of Contracts 8vo, 

Winthrop's Abridgment of Military Law i2mo, 

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MANUFACTURES. 

Bernadou's Smokeless Powder— Nitro-cellulose and Theory of the Cellulose 

Molecule 1 2mo, 2 50 

Bolland's Iron Founder i2mo, 2 50 

"The Iron Founder," Supplement i2mo, 2 50 

Encyclopedia of Founding and Dictionary of Foundry Terms Used in the 

Practice of Moulding i2mo, 3 00 

* Eckel's Cements, Limes, and Plasters 8vo, 6 00 

Eissler's Modern High Explosives 8vo, 4 00 

Effront's Enzymes and their Applications. (Prescott.) 8vo, 3 00 

Fitzgerald's Boston Machinist i2mo, i 00 

Ford's Boiler Making for Boiler Makers iSmo, i 00 

Hopkin's Oil-chemists' Handbook Svo, 3 00 

Keep's Cast Iron Svo, 2 50 

Leach's The Inspection and Analysis of Food with Special Reference to State 

Control Large Svo, 7 50 

* McKay and Larsen's Principles and Practice of Butter-making Svo, i 50 

Matthews's The Textile Fibres Svo, 3 50 

Metcalf's Steel. A Manual for Steel-users i2mo, 2 00 

Metcalfe's Cost of Manufactures — And the Administration of Workshops. Svo, 5 00 

Meyer's Modern Locomotive Construction 4to, 10 00 

Morse's Calculations used in Cane-sugar Factories i6mo, morocco, i 50 

* Reisig's Guide to Piece-dyeing Svo, 25 00 

Sabin's Industrial and Artistic Technology of Paints and Varnish Svo, 3 00 

Smith's Press-working of Metals Svo, 3 00 

Spalding's Hydraulic Cement i2mo, 2 00 

Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, morocco, 3 00 

Handbook for Cane Sugar Manufacturers i6mo, morocco, 3 00 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced Svo, 5 00 

Thurston's Manual of Steam-boilers, their Designs, Construction and Opera- 
tion Svo, 5 00 

* Walke's Lectures on Explosives Svo, 4 00 

Ware's Beet-sugar Manufacture and Refining Small Svo, 4 00 

West's American Foundry Practice i2mo, 2 50 

Moulder's Text-book i2mo, 2 50 

Wolff's Windmill as a Prime Mover Svo, 3 00 

Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. .Svo, 4 00 

MATHEMATICS. 

Baker's Elliptic Functions Svo, 

* Bass's Elements of Differential Calculus i2mo, 

Briggs's Elements of Plane Analytic Geometry i2mo, 

Compton's Manual of Logarithmic Computations i2mo, 

Davis's Introduction to the Logic of Algebra Svo, 

* Dickson's College Algebra Large i2mo, 

* Introduction to the Theory of Algebraic Equations Large i2mo, 

Emch's Introduction to Projective Geometry and its Applications Svo, 

Halsted's Elements of Geometry Svo, 

Elementary Synthetic Geometry .Svo, 

Rational Geometry i2mo, 

* Johnson's (J. B.) Three-place Logarithmic Tables: Vest-pocket size. paper, 

100 copies for 

* Mounted on heavy cardboard, SXio inches, 

10 copies for 
Johnson's (W. W.) Elementary Treatise on Differential Calculus. Small Svo, 

Elementary Treatise on the Integral Calculus Small Svo, 

11 



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Johnson's (W. W.) Curve Tracing in Cartesian Co-ordinates .i2nio, i oo 

Johmson's (W. W.) Treatise on Ordinary and Partial Differential Equations. 

Small 8vo, 3 50 
Johnson's (W. W.) Theory of Errors and the Method of Least Squares. i2mo, i 50 

* Johnson's (W. W.) Theoretical Mechanics i2mo, 3 00 

Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . i2mo, 2 00 

* Ludlow and Bass. Elements of TrigoHometry and Logarithmic and Other 

Tables 8vo, 3 00 

Trigonometry and Tables published separately Each, 2 00 

* Ludlow's Logarithmic and Trigonometric Tables 8vo, i 00 

Mathematical Monographs. Edited by Mansfield Merriman and Robert 

S. Woodward Octavo, each i 00 

No. I. History of Modern Mathematics, by David Eugene Smith. 
No. 2. Synthetic Projective Geometry, by George Bruce Halsted. 
No. 3. Determinants, by Laenas Gifford Weld. No. 4. Hyper- 
bolic Functions, by James McMahon. No. 5. Harmonic Func- 
tions, by William E. Byerly. No. 6. Grassmann's Space Analysis, 
by Edward W. Hyde. No. 7. Probability and Theory of Errors, 
by Robert S. Woodward. No. 8. Vector Analysis and Quaternions, 
by Alexander Macfarlane. No. 9. Differential Equations, by 
William Woolsey Johnson, No. 10. The Soluti®n of Equations, 
by] Mansfield Mernman. No. 11. Functions of a Complex Variable, 
by Thomas S. Fiske. 

Maurer's Technical Mechanics 8vo, 4 00 

Merriman's Method of Least Squares 8vo, 2 00 

Rice and Johnson's Elementary Treatise on the Differential Calculus. . Sm. 8vo, 3 00 

Differential and Integral Calculus. 2 vols, in one Small 8vo, 2 50 

Wood's Elements of Co-ordinate Geometry 8vo, 2 00 

Trigonometry: Anal3rtical, Plane, and Spherical i2mo, i 00 



MECHANICAL ENGINEERING. 

MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS. 

Bacon's Forge Practice i2mo, 

Baldwin's Steam Heating for Buildings i2mo, 

Barr's Kinematics of Machinery 8vo, 

* Bartlett's Mechanical Drawing 8vo, 

* " " " Abridged Ed 8vo, 

Benjamin's Wrinkles and Recipes i2mo, 

Carpenter's Experimental Engineering 8vo, 

Heating and Ventilating Buildings 8vo, 

Gary's Smoke Suppression in Plants using Bituminous Coal. (In Prepara- 
tion.) 

Clerk's Gas and Oil Engine Small 8vo, 4 00 

Coolidge's Manual of Drawing .8vo, paper, i 00 

Coolidge and Freeman's Elements of General Drafting for Mechanical En- 
gineers Oblong 4to, 2 so 

Cromwell's Treatise on Toothed Gearing i2mo, i 50 

Treatise on Belts and Pulleys i2mo, i 50 

Durley's Kinematics of Machines 8vo, 4 00 

Flather's Dynamometers and the Measurement of Power. . i2mo, 3 00 

Rope Driving i2mo, 2 00 

Gill's Gas and Fuel Analysis for Engineers i2mo, i 25 

Hall's Car Lubrication i2mo, i 00 

Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 

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Button's The Gas Engine 8vo, 

Jamison's Mechanical Drawing 8vo, 

Jones's Machine Design: 

Part I. Kinematics of Machinery. 8vo, 

Part II. Form, Strength, and Proportions of Parts Svo, 

Kent's Mechanical Engineers' Pocket-book i6mo, mor»cco, 

Kerr's Power and Power Transmission Svo, 

Leonard's Machine Shop, Tools, and Methods Svo, 

* Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean.) . . Svo, 
MacCord's Kinematics; or, Practical Mechanism Svo, 

Mechanical Drawing 4to, 

Velocity Diagrams Svo, 

MacFarland's Standard Reduction Factors for <Jases Svo, 

Mahan's Industrial Drawing. (Thompson.) Svo, 

Poole's Calorific Power of Fuels Svo, 

Reid's Course in Mechanical Drawing Svo, 

Text-book of Mechanical Drawing and Elementary Machine Design. Svo, 

Richard's Compressed Air lamo, 

Robinson's Principles of Mechanism Svo, 

Schwamb and Merrill's Elements of Mechanism Svo, 

Smith's (O.) Press-working of Metals Svo, 

Smith (A. W.) and Marx's Machine Design Svo, 

Thurston's Treatise on Friction and Lost Work in Machinery and Mill 
Work Svo, 

Animal as a Machine and Prime Motor, and the Laws of Energetics. i2mo, 

Warren's Elements of Machine Construction and Drawing Svo, 

Weisbach's Kinematics and the Power of Transmission. (Herrmann — 
Klein.) Svo, 

Machinery of Transmission and Governors. (Herrmann — Klein.). Svo, 

Wolff's Windmill as a Prime Mover Svo, 

Wood's Turbines. Svo, 



MATERIALS OP ENGINEERING. 

* Bovey's Strength of Materials and Theory of Structures Svo, 7 50 

Burr's Elasticity and Resistance of the Materials of Engineering. 6th Edition. 

Reset Svo, 

Church's Mechanics of Engineering Svo, 

* Greene's Structural Mechanics Svo, 

Johnson's Materials of Construction Svo, 

Keep's Cast Iron Svo, 

Lanza's Applied Mechanics Svo, 

Martens's Handbook on Testing Materials. (Henning.) Svo, 

Maxirer's Technical Mechanics Svo, 

Merriman's Mechanics of Materials Svo, 

Strength of Materials i2mo, 

Metcalf's Steel. A manual for Steel-users i2mo, 

Sabin's Industrial and Artistic Technology of Paints and Varnish Svo, 

Smith's Materials of Machines izmo, 

Thurston's Materials of Engineering 3 vols., Svo, 

Part II. Iron and Steel Svo, 

Part in. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents Svo, 

Text-book of the Materials of Construction Svo, 

Wood's (De V.) Treatise on the Resistance of Materials and an Appendix on 

the Preservation of Timber Svo, 

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Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 00 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel 8vo, 4 00 



STEAM-ENGINES AND BOILERS. 

Berry's Temperature-entropy Diagram i2mo, 1 25 

Carnot's Reflections on the Motive Power of Heat. (Thurston.) i2mo, i 50 

Dawson's "Engineering" and Electric Traction Pocket-book. . . .i6mo, mor., 5 00 

Ford's Boiler Making for Boiler Makers i8mo, i 00 

Goss's Locomotive Sparks Svo, 2 00 

Hemenway's Indicator Practice and Steam-engine Economy i2mo, 2 00 

Button's Mechanical Engineering of Power Plants Svo, 5 00 

Heat and Heat-engines Svo, 5 00 

Kent's Steam boiler Economy ." Svo, 4 00 

Kneass's Practice and Theory of the Injector Svo, i 50 

MacCord's Slide-valves Svo, 2 00 

Meyer's Modern Locomotive Construction 4to, 10 00 

Peabody's Manual of the Steam-engine Indicator i2mo, i 50 

Tables of the Properties of Saturated Steam and Other Vapors Svo, i 00 

Thermodynamics of the Steam-engine and Other Heat-engines Svo, 5 00 

Valve-gears for Steam-engines Svo, 2 50 

Peabody and Miller's Steam-boilers Svo, 4 00 

Pray's Twenty Years with the Indicator Large Svo, 2 50 

Pupin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. 

(Osterberg.) i2mo, i 25 

Reagan's Locomotives: Simple Compound, and Electric i2mo, 2 50 

Rontgen's Principles of Thermodynamics. (Du Bois.) '. . . .Svo, 5 00 

Sinclair's Locomotive Engine Running and Management i2mo, 2 00 

Smart's Handbook of Engineering Laboratory Practice i2mo, 2 50 

Snow's Steam-boiler Practice Svo, 3 00 

Spangler's Valve-gears Svo, 2 50 

Notes on Thermodynamics i2mo, i 00 

Spangler, Greene, and Marshall's Elements of Steam-engineering Svo, 3 00 

Thomas's Steam-turbines Svo, 3 50 

Thurston's Handy Tables Svo, i 50 

Manual of the Steam-engine 2 vols., Svo, 10 00 

Part I. History, Structure, and Theory Svo, 6 00 

Part II. Design, Construction, and Operation Svo, 6 00 

Handbook of Engine and Boiler Trials, and the Use of the Indicator and 

the Prony Brake Svo, 5 00 

Stationary Steam-engines Svo, 2 50 

Steam-boiler Explosions in Theory and in Practice i2mo, i 50 

Manual of Steam-boilers, their Designs, Construction, and Operation Svo, 5 00 

Weisbach's Heat, Steam, and Steam-engines. (Du Bois.) Svo, 5 00 

Whitham's Steam-engine Design Svo, 5 00 

Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. . .Svo, 4 00 



MECHANICS AND MACHINERY. 

Barr's Kinematics of Machinery Svo, 2 50 

*, Bovey's Strength of Materials and Theory of Structures Svo, 7 50 

Chase's The Art of Pattern-making i2mo, 2 50 

Church's Mechanics of Engineering Svo, 6 00 

Notes and Examples in Mechanics Svo, 2 00 

Compton's First Lessons in Metal-working i2mo, i 50 

Compton and De Groodt's The Speed Lathe i2mo i 50 

14 



Cromwell's Treatise on Toothed Gearing i2mo, i 50 

Treatise on Belts and Pulleys i2mo, : 50 

Dana's Text-book of Elementary Mechanics for Colleges and Schools. . i2mo, i 50 

Dingey's Machinery Pattern Making i2mo, 2 00 

Dredge's Record of the Transportation Exhibits Building of the World's 

Columbian Exposition of 1893 4to half morocco, 5 00 

Du Bois's Elementary Principles of Mechanics: 

Vol. I. Kinematics 8vo, 

Vol. II. Statics 8vo, 

Mechanics of Engineering. Vol. I Small 4to, 

Vol. II Small 4to, 

Durley's Kinematics of Machines 8vo, 

Fitzgerald's Boston Machinist i6mo, 

Flather's Dynamometers, and the Measurement of Power i2mo. 

Rope Driving i2mo, 

Goss's Locomotive Sparks 8vo, 

* Greene's Structural Mechanics Svo, 

Hall's Car Lubrication 1 2mo, 

Holly's Art of Saw Filing iSmo, 

James's Kinemr.tics of a Point and the Rational Mechanics of a Particle. 

Sma.l Svo, 

* Johnson's (W. W.) Theoretical Mechanics i2mo, 

Johnson's (L. J.) Statics by Graphic and Algebraic Methods Svo, 

Jones's Machine Design : 

Part I. Kinematics of Machinery Svo, 

Part II. Form, Strength, and Proportions of Parts Svo, 

Kerr's Power and Power Transmission Svo, 

Lanza's Applied Mechanics Svo, 

Leonard's Machine Shop, Tools, and Methods Svo, 

* Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean.). Svo, 
MacCord's Kinematics; or. Practical Mechanism Svo, 

Velocity Diagrams Svo, 

Maurer's Technical Mechanics Svo, 

Merriman's Mechanics of Materials Svo, 

* Elements of Mechanics i2mo, 

* Michie's Elements of Analytical Mechanics Svo, 

Reagan's Locomotives: Simple, Compound, and Electric i2mo, 

Reid's Course in Mechanical Drawing Svo, 

Text-book of Mechanical Drawing and Elementary Machine Design. Svo, 

Richards's Compressed Air -. i2mo, 

Robinson's Principles of Mechanism Svo, 

Ryan, Norris, and Hoxie's Electrical Machinery. Vol. I Svo, 

Schwamb and Merrill's Elements of Mechanism Svo, 

Sinclair's Locomotive-engine Running and Management i2mo. 

Smith's (0.) Press-working of Metals Svo, 

Smith's (A. W.) Materials of Machines i2mo. 

Smith (A. W.) and Marx's Machine Design Svo, 

Spangler, Green*, and Marshall's Elements of Steam-engineering Svo, 

Thurston's Treatise on Friction and Lost Work in Machinery and Mill 

Work Svo, 3 00 

Animal as a Machine and Prime Motor, and the Laws of Energetics. 

i2mo, 

Warren's Elements of Machine Construction and Drawing Svo, 

Weisbach's Kinematics and Power of Transmission. (Herrmann — Klein.) . Svo, 

Machinery of Transmission and Governors. (Herrmann — Klein.). Svo, 
Wood's Elements of Analytical Mechanics Svo, 

Principles of Elementary Mechanics i2mo. 

Turbines. Svo, 

The World's Cohimbian Exposition of 1893 4to, 

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METALLURGY. 

Egleston's Metallurgy of Silver, Gold, and Mercury: 

Vol. I. Silver 8vo, 

Vol. n. Gold and Mercury Svo, 

** Iles's Lead-smelting. (Postage g cents additional.) i2mo, 

Keep's Cast Iron Svo, 

Kunhardt's Practice of Ore Dressing in Europe Svo, 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess. )i2mo. 

Metcalf's Steel. A Manual for Steel-users i2mo, 

Minet's Production of Aluminum and its Industrial Use. (Waldo.). . . . lamo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc.) Svo, 

Smith's Materials of Machines i2mo, 

Thurston's Materials of Engineering. In Three Parts Svo, 

Part II. Iron and Steel Svo, 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents Svo, 

Ulke's Modern Electrolytic Copper Refining Svo, 



MINERALOGY. 



Barringer's Description of Minerals of Commercial Value. Oblong, morocco, 

Boyd's Resources of Southwest Virginia Svo, 

Map of Southwest Virignia Pocket-book form. 

Brush's Manual of Determinative Mineralogy. (Penfield.) Svo, 

Chester's Catalogue of Minerals Svo, paper. 

Cloth, 

Dictionary of the Names of Minerals Svo, 

Dana's System of Mineralogy Large Svo, half leather, 

First Appendix to Dana's New " System of Mineralogy." Large Svo, 

Text-book of Mineralogy Svo, 

Minerals and How to Study Them i2mo, 

Catalogue of American Localities of Minerals Large Svo, 

Manual of Mineralogy and Petrography i2mo, 

Douglas's Untechnical Addresses on Technical Subjects i2mo, 

Eakle's Mineral Tables Svo, 

Egleston's Catalogue of Minerals and Synonyms Svo, 

Hussak's The Determination of Rock-forming Minerals. (Smith.).SmaU Svo, 
Merrill's Non-metallic Minerals: Their Occurrence and Uses Svo, 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

Svo, paper, 50 
Rosenbusch's Microscopical Physiography of the Rock-making Minerals. 

(Iddings.) Svo, 5 00 

* Tillman's Text-book of Important Minerals and Rocks Svo, 2 00 



MINING. 

Beard's Ventilation of Mines i2mo, 2 50 

Boyd's Resources of Southwest Virginia Tvo, 3 00 

Map of Southwest Virginia Pocket-book form 2 00 

Douglas's Untechnical Addresses on Technical Subjects i2mo. i 00 

* Drinker's Tunneling, Explosive Compounds, and Rock Drills. 4to,hf. mor., 25 00 

Eissler's Modern High Explosives Svo, 4 00 

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Goodyear's Coal-mines of the Western Coast of the United States i2mo, 

Ihlseng's Manual of Mining 8vo, 

** Iles's Lead-smelting. (Postage 9c. additional.) i2mo, 

Kunhardt's Practice of Ore Dressing in Europe 8vo, 

O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc.) Svo, 

* Walke's Lectures on Explosives Svo, 

Wilson's Cyanide Processes i2mo, 

Chlorination Process ■ i2mo, 

Hydraulic and Placer Mining i2mo, 

Treatise on Practical and Theoretical Mine Ventilation X2mo, i 25 



SANITARY SCIENCE. 

Bashore's Sanitation ©f a Country House i2mo, 

Folwell's Sewerage. (Designing, Construction, and Maintenance.) Svo, 

Water-supply Engineering Svo, 

Fowler's Sewage Works Analyses i2mD, 

Fuertes's Water and Public Health i2mo, 

Water-filtration Works i2mo, 

Gerhard's Guide to Sanitary House-inspection i6mo, 

Goodrich's Economic Disposal of Town's Refuse Demy Svo, 

Hazen's Filtration of Public Water-supplies Svo, 

Leach's The Inspection and Analysis of Food with Special Reference to State 

Control Svo, 

Mason's Water-supply. (Considered principally from a Sanitary Standpoint) Svo, 

Examination of Water. (Chemical and Bacteriological.) i2mo, 

Ogden's Sewer Design i2mo, 

Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- 
ence to Sanitary Water Analysis izmo, 

* Price's Handbook on Sanitation i2mo, 

Richards's Cost of Food. A Study in Dietaries i2mo, 

Cost of Living as Modified by Sanitary Science i2mo. 

Cost of Shelter i2mo, 

Richards and Woodman's Air, Water, and Food from a Sanitary Stand- 
point Svo, 

* Richards and Williams's The Dietary Computer Svo, 

Rideal's Sewage and Bacterial Purification of Sewage Svo, 

Turneaure and Russell's Public Water-supplies Svo, 

Von Behring's Suppression of Tuberculosis. (Bclduan.) i2mo, 

Whipple's Microscopy of Drinking-water Svo, 

Winton's Microscopy of Vegetable Foods Svo, 

Woodhull's Notes on Military Hygiene i6mo, 

* Personal H/giene i2mo, 



MISCELLANEOUS. 

De Fursac's Manual of Psychiatry. (Rosanoff and Collins.). . . .Large i2mo, 2 50 
Emmons's Geological Guide-hook of the Rocky Mountain Excursion of the 

International Congress of Geologists. Large Cvo, i 50 

Ferrel's Popular Treatise on the Winds Svo 4 00 

Haines's American Railway Management i2mo, 2 50 

Mott's Fallacy of the Present Theory of Sound i6mo, i 00 

Ricketts's History of Rensselaer Polytechnic Institute, 1S24-1S94. .Small Svo, 3 oc 

Rostoski's Serum Diagnosis. (Bolduan.) i2mo. i 00 

Rotherham's Emphasized New Testament Large Svo, 2 00 

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Steel's Treatise on the Diseases of the Dog 8v©, 3 50 

The World's Columbian Exposition of 1893 4to, i 00 

Von Behring's Suppression ot Tuberculosis. (Bolduan.) i2mo, i 00 

Winslow's Elements of Applied Microscopy i2mo, i 50 

Worcester and Atkinson. Small Hospitals, Establishment and Maintenance; 

Suggestions for Hospital Architecture : Plans for Small Hospital . i2mo, i 25 



HEBREW AND CHALDEE TEXT-BOOKS. 



Green's Elementary Hebrew Grammar i2mo, i 25 

Hebrew Chrestomathy 8vo, 2 00 

Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scriptures. 

(Tregeiles.) Small 4to, half morocco, 5 00 

Letteris's Hebrew Bible 8vo, 2 25 

18 



JUN 4 U^tr. 



i!Uiuniui;uui_:i:i:.. i_ _.L 

LIBRARY OF CONGRESS 



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